Emergency Gas Leak repair in south London

During an emergency gas leak repair in south London the other day, I came across a textbook example of how important it is to act immediately when you smell gas. Luckily, the first thing the owners did was call the Emergency Service Provider, or ESP for short, when they thought they could smell something. Contrary to what a lot of people think, this is NOT British Gas or the gasboard.

The Emergency Service Provider is the a free service that anyone can call, regardless of whether you are the owner, tenant, visitor or even just somebody who walks somewhere and thinks there is a gas smell somewhere. Although the company that will actually attend to the suspected gas escape differs from area to area, the number to call anywhere on the English mainland is 0800 111 999. In south London, it is National Grid that is responsible for attending to potential gas escapes but it may be a contractor like Morrisons that will send an engineer out.

In this case, it was the contractor that knocked on the door within half an hour of the smell being reported (they usually are very quick indeed). He tried to locate the leak but was not able to do that in the limited amount of time available and therefore had no other option than to make the situation safe by isolating the gas. The owner then called me and I went a couple of hours later to find out where the leaking gas came from.


 As a gasboiler repair specialist, I have very sensitive electronic equipment that can help me trace the source of the gas escape even if it is extremely small. In this case, after I had reinstated the supply, I could detect a slight smell of gas confirming that there actually was a problem but it wasn’t very strong. No doubt some people would have considered this only minor smell to be something not very dangerous and kept the gas on over the weekend to avoid extra cost or inconvenience. In cases like this one, that could turn into a disaster.

What had happened, was a slow rotting away from a gaspipe partially buried in cement until the surface was wafer thin and the first pin prick hole appeared causing the slight smell. When I moved the washing machine to get to it, the pipe moved also and the pin prick size hole became a much wider crack nearly an inch long. If that had slight knock had not been me but the washing machine shaking a bit during the wash, a lot of gas would have escaped creating a very dangerous situation very quickly.

The moral of this story is to err on the side of caution and call the Gas Emergency number 0800 111 999 when you think you MAY smell gas. It won’t cost you anything irrespective of time or day and regardless of whether they find a leak or not, and nobody will blame you for being cautious.

Why not check right now to make sure the free gas leak emergency number for south London is clearly displayed on or near your gas meter, so it you know where to find it if there is a problem one day.

Requirements for a CP12

Landlords need a new CP12 every year to verify that the gas-installation in the properties they rent out to tenants is safe and this is known by virtually all concerned, at least in south London where I work. What exactly must be inspected is a lot less clear and how it should be done is an even greater source of confusion. There is a number of reasons why the situation became like it is, but the main reasons are that the law in itself only states very generic items and the guidance documents have an awful lot of “should” in them. A simple example is in the law states landlord must ensure that the gas-installation is maintained to a safe standard, but it doesn’t say what is required to comply with that rule. There is mention for example of “reasonable steps” that must be taken. A bit further it continues with : ‘maintenance “normally involves an “ongoing” programme of regular/periodic inspections’. What is regular, or periodic? A quick look to see if the boiler is still there on the January 2nd of the first year is regular, periodic and ongoing but I doubt it would suffice to make sure the installation is safe.

To make sure as a landlord that you have complied with the requirement to produce a landlord gas safety certificate for your tenants every year, all you have to do is make sure that the gas-installer that does the inspection is on the list of the Gas Safe Register. It is NOT Corgi any more, they were booted about 5 years ago. The name still exists, but it is a commercial company just like any other company, despite what some of the people that work for the company or use the company’s logo may want you to believe. From all I’ve been able to find out, as long as the chap that ‘signs off’ the CP12 is on the GSR list, the landlord is in the clear even if the inspection is not up to spec. This seems to entice some landlords that value a low price higher than safety, to hire the cheapest they can find because the certificate is all they are interested in.

This practice may prove a costly mistake because it may cover the landlord on the requirement to produce this landlord gas safety certificate, it does NOT discharge them of the obligation to maintain the gas installation to a safe standard. Like a car MOT, the certificate only states what the inspector found on that day, nothing more and nothing less. If there is an incident where escaping gas or fumes injure a tenant, the landlord will find himself almost surely in court and will be extremely unlikely to escape a conviction. Any time somebody is taken to hospital in an ambulance, which is pretty much standard procedure these days, because of suspected CO poisoning or gas burns, an automatic compulsory HSE investigation is triggered. It doesn’t matter whether or not the CO poisoning was real or that something else caused the symptoms either, ambulance + suspicion = HSE investigation.

If evidence is found that the gas-installation maintenance was lacking (and if it was poor, they will almost certainly find it) the costs to the landlord will be an awful lot higher than the “savings” made by not having the installation serviced. Next week I will go into the how and what of maintenance a bit further.

Saving money on gas by reducing boiler use

With household fuel bills at an all time high, I get more and more people asking me how much it would be to install a fire when I am there to service or repair their boiler here in south London. The logic seems obvious: if I heat just one room with a small fire then that must be cheaper than turning the boiler on. You would save money if a fire and a central heating boiler worked in the same way, but they don’t. The only ways to save money on your gasbill without large costs first are using the heating less, and make sure the system is used as economically as possible. Practical tips on how to do that are here.


That is to say, very old ones do but the rest don’t. In the old days when back boilers like the old Baxi Bermuda, you could indeed save money by leaving the boiler off and just using the fire and heat the living room. But that was only because the boiler, the fire, the flue and the ventilation were all in the same room, so nothing else changed.


The vast majority of boiler have been roomsealed for some twenty years, and all of them for the last ten. Apart from a number of other technical advantages, that means there is no need for a flue opening through which heat escapes from the room, nor is a ventilation opening in the room needed. Apart from fairly rare wall heating units with a balanced or fan-assisted flue, fires need a permanently open flue/chimney to dispose of the fumes, and a lot of decorative ones, the type that simulate a wood or coal fire, also need a permanent ventilation opening to provide oxygen for the combustion of the gas.

The open flue which is uncontrolled is the main reason that ‘normal’ fires are only about 60% efficient in heating the room, the other 40% goes literally up in smoke and out the chimney. But that isn’t where the downsides end. It is illegal to have a closable flue/chimney on a gas fire, which means that during the hours the fire is off, the flue is still creating more draft that causes the room to lose heat. This will actually make the room colder or alternative cold earlier and this will entice you to light the fire or turn the boiler on more and/or sooner.

There a number of reasons to have a gas fire; most of them look quite nice these days, they create focal point in the room and give that cosy feeling of huddling up around the fire. There is however one thing they do not do with the exception maybe of the aforementioned sealed models: saving you money. Due to the nature of the setup it isn’t really possible to actually calculate the costs, but I’d hazard a guess that the additional cost of having a gas fire is £100 per year when you add the lower efficiency to the permanent heat loss created by the open chimney.

What would I do to save money on my gas? Change gas supplier every year the moment the winter tariffs have been announced.

CP12 and electrical bonding of the gas pipe

The role electrical bonding plays in a CP12 is largely misunderstood and often misquoted. Legally there is no requirement to check anything to do with electricity when a heating engineer does an inspection for Landlord Gas Safety Certificate because the GSIUR do not specify any requirement to check it. What is more, unless a heating engineer is also a trained electrician, he isn’t actually qualified to check for gas pipe bonding in terms of wiring. To top this up, electrical inspections require specialist and expensive equipment which the average heating engineer would have no need for.

In the whole of the gas legislation, the Gas Safety Installation and Use Regulations as the GSIUR are called in full, only specifies in section 18 the requirement for the gas installer to notify the responsible person that the installation of electrical bonding to the gaspipe may be necessary when he connects gaspipework to the gasmeter. It may be good common practice to check for the presence of bonding when you do work on a gas installation or carry out a safety inspection to see if this vital part of electrical safety is present, but that is where it ends. If the bonding does not appear present, it can me mentioned on the CP12 form, but it certainly does not automatically  mean the gas installation is unsafe for the tenant to use.

This page has a direct link to the full GSIUR  text:


Presuming for the purpose of this exercise that the gas installer who carries out the inspection is only qualified and registered to work on gas, (as is the case in the vast majority of heating engineers) he should not ‘check’ if the bonding is correct as he is neither qualified nor equipped to do so.

As a gas user, whether that is as tenant, landlord or owner/occupier, you can very simply check if the bonding is present and if it looks like it meets the requirements.

Where should the bonding be?

For ‘indoor’ meters, it should be less than 600 mm away from the meter, or about two feet in old money, and BEFORE the first tee. It should be connected with a suitable clamp to BS 951 which is not the same as a garden hose clamp, and on a clean metal surface. A clamp attached to painted or coated pipe is unlikely to do the job. The required minimum size is usually 10 SQUARE millimetres which is just under 4 mm thickness of the actual cable without insulation.

For ‘outdoor’ gas meters, the ones that are in the box on the wall or half in the ground, the requirements are the same apart from the distance to the meter. It can be within 600 mm and before the first tee and then led indoors in an appropriate way, or the cable can be connected to the pipe as close as is practicable to where it enters the property. Especially the latter can be not all that obvious, so if you don’t see the cable, it doesn’t meant it isn’t there. When you can see the cable, it doesn’t necessarily mean it actually works as it is designed to do. This is the reason that bonding doesn’t way very heavily for gas installers and why it is a good idea to have the electricity in your home inspected from time to time by somebody who is properly qualified and equipped to do so instead of leaving only to be checked for the annual CP12.

Free Green Deal boiler installs in south London

Another question I hear on a regular basis in south London when I go around repairing boilers, is whether it wouldn’t be better to scrap the old one and stick a new model in. Somehow often soon followed by: ”how about those ‘free’ boilers from Green Deal”?

This immediately displays the first common misunderstanding about the subject: Green Deal boilers are certainly not free, they aren’t even cheap. All it is, is ‘guaranteed’ loan scheme, and a very costly one at that. For starters, not everyone qualifies. To see if you qualify, you first need to book a visit from an approved ‘assessor’. Prices vary but the most common one I’ve heard is a hundred quid, or more strategically marketed as £99.99. Not approve? Money gone.

If you ‘are approved’ you can only use installers that are part of the club. These ‘approved’ installers had to make considerable investments to join the elite and therefore don’t come cheap. On top of the fact that there is not much chance of a good price for the job, there is the cost of the loan as well as the cost of ‘brokering’ the loan. The interest rate is neither particularly good, nor is it inflation proof as far as I have been able to find out. Currently, the minister of propaganda thinks “it is reasonable” to expect about 15 times the base rate but won’t exclude 20 times.

That means if we take an expected average price of around £4000 instead of the normal £2000, and add the interest of anywhere from £1500 to £2500, you end up with a total cost of the boiler somewhere in the region of £6000 i.e. two to three times the average price.

This is only part of the reason why the Green Deal boiler install finance scheme is a total fiasco judging by the figures available. Presumably to safe face, the figures are hard to find, not exactly consistent and appear to have been treated with all the spin available. I have found: people have now been able to sign up for 15 months during which (and before) millions of pounds have been spent on promoting of it. During this time, well over 100,000 “assessments” have been carried out. Thirty-odd boilers have been installed by means of the Green Deal finance scheme. The DECC, Department of Energy and Climate Change did not have the figures available when I contacted them, but promised to see what they could do. The Secretary of State for Energy and Climate Change, the right honourable Ed Davey stated around April last year after much resistance that he expected at least 10,000. Maybe I missed it, but I can’t find any more recent statements from him about the numbers that should be achieved about Green Deal finance for boiler installs.

Now you know why the vast majority of people I see in south London still think it’s a far better idea to repair their boiler than to replace it.

Boiler repairs due to corrosion

During the many years I have been repairing boilers in and around south London, it has become clear that there is one cause for problems and faults that probably costs home owners more than the second, third and forth reasons combined. Cutting corners.

We all like to pay less and I love a bargain as much as you if not more, but ‘saving money’ by not doing what should be done with central heating is bad news and very expensive in the long run. The most common problem stemming from sloppy work is damage done by dirt in the system. It starts with installation or repair work that is not done properly and then is allowed to get worse because it is not spotted due to poor maintenance.

When any soldering work is done on any part of the system, flux residue ends up in the water. This is a corrosive and usually acidic substance that ‘attacks’ the metal parts of the system and multiplies the level of corrosion. Apart from this corrosion eating away your boiler, pipes and radiators, it also forms a specific form of black rust called magnetite. Contrary to the brownish form of rust that is loose and/or flaky, magnetite is a fairly strong substance. Apart from being easily strong enough not to crack or break by warming up and cooling down, or vibrations and mechanical shocks, magnetite formations also attract other magnetite particles in the water.

In traditional systems with a tank in the loft and a cylinder in the airing cupboard, the tends to cause blockages near the pump, wear the pump out and damage the zone valves. Eventually, it starts to cause ‘pumping over’ in the tank, which in turn significantly speeds up the corrosion and it won’t be long before the system stops working. From there on, the breakdowns will occur more and more frequently until the underlying reason of the problem is removed.

In sealed combi systems the most common symptoms are problems with the hot water becoming poor or intermittent. The usual suspects are the heat exchanger, diverter valve and pump. As with the problems for the open vent system, simply replacing the broken part is more likely than not only a temporary solution and the problem is bound to come back.

How does boiler maintenance prevent this, you may ask. Servicing PROPERLY is more than a quick probe in the flue and take a few measurements as is commonly done by Biggish Gas companies that offer “boiler service” contracts. Their methods may meet the legal requirements, but they don’t offer good value for money in my humble opinion. When I service a boiler, I open it up and clean it out. I check the pressure in the expansion vessel and look for signs of leaks. I also check the water in the system for contaminants and verify that the radiators and hot water production are up to spec. By doing things like that, I find the beginning of a problem when it is usually quick and cheap to fix and can prevent further damage and expensive boiler repairs.

Does a landlord need a new CP12 before different tenants move in?

One of the issues that causes lots of uncertainty for landlords, is the question what needs to be done when one tenant leaves the property and the next one moves in. The most common question being:

Q: Do I need a new CP12?

A: The existing one remains valid until the original ‘expiry date’.

Q: So I can just let the new tenants move in?

A: Not quite. The landlord MUST make sure that the entire gas-installation i.e. ALL appliances that are there, flues, ventilation and gaspipes are safe. People that move out can damage things unintentionally or out of spite.

One example is a free standing cooker that is removed by disconnecting it from the bayonet connector. There is no law that literally says that the landlord needs to engage a Registered Gas Installer to check these things, but it may be a bit difficult to defend a diy job in verifying that there is no gasleak if you’re not qualified to work on gas.

Another point is ventilation. A lot of non-roomsealed appliances need a certain amount of ventilation and it is not always obvious if the vents are adequate and/or working correctly. I have seen many a vent blocked by people because they did not like the draft they caused. Understandable, but dangerous and easy to miss. Lack of adequate ventilation leads all too often to carbon monoxide development and the results of that can be lethal.

Unfortunately, the way the legislation is worded leaves a lot of room for uncertainty about what exactly is required and what is optional. I have been repairing boilers and servicing them in south London for many years, spent countless hours discussing the requirements and still don’t have 100% of the answers to the countless questions about the details. Apparently I am not the only one; the ‘official guidance’ on how to interpret the rules and regulations on the subject is changed on a very regular basis.

If a cavalier attitude to gas is risky, taking chances with CP12′s and gas safety checks before new tenants move in, is a really bad idea for landlords for several reasons.

  1. Complaints from tenants are treated as a high priority; there is a free phone number they can call for a free inspection and not a whole lot of questions are asked before the inspector is booked for a visit.
  2. As mentioned above, it is a bit of a minefield and quite easy to fall short of the requirements.
  3. As a lot of the compulsory safety checks must be done with every service and almost every boiler repair, there is a large overlap. This makes adding a service to a CP12 or vice versa very cheap and the same goes for an gas safety inspection before a new tenant moves in or a repairing the boiler. Combining 2 of the options at one visit will usually drop the price of the second ‘job’ by half, if not more, bringing the cost to the landlord down to a couple of quid per month rent without any concessions to the quality of either and that is without taking into account the money saved by boiler breakdown prevention as a result of proper servicing.

Boiler repair quotes by phone

As a boiler repair specialist in south London, despite many years of experience there is still one question that I get on a regular basis and still can’t answer when people call me. You may wonder why somebody who has been doing the same job for so long still can not answer the most commonly asked question, but the answer is simple: I’m a heating engineer, not a fortune teller. When a home owner calls me, the first question tends to be: “Can you repair it?” After making sure that they do not have one of the rare models for which I simply can not get any spares, they seem quite happy when I tell them that I am pretty sure I can. In fact, so sure that I guarantee there will be no charge if I can not find the problem.

The next question tends to be: “How much will it cost?” Unfortunately, without knowing why the central heating has broken down, I don’t know which part of the boiler need to be repaired or replaced. That also means I don’t know whether it will take 10 minutes of 5 hours. Without having any idea about the cost of the parts or the amount time needed, I can’t even give an estimate, or a maximum. What is more, NOBODY can. The obvious question here is: why can’t you give me a price when others can?

The answer, again, is simple: they can’t. We CAN give you an average, but that is about as much use as the average family size of 1.8 children. Could be me, but I don’t know anyone in real life who actually has exactly 1.8 children. Another option is some nonsense like: “COULD be the so-and-so or the watchammacallit, that will be about so much to sort out. True, it COULD be, but more likely than not it is something else.

There is only one REAL way of giving a price over the phone, and that is the Fixed-Fee-Repair. The way they are sold, they sound like a no-brainer. “Guaranteed” repair, “no matter what is wrong” for £79. If it sounds to good to be true, it usually isn’t true. Not surprisingly, there are a few catches with this wonderful offer.

First of all, it isn’t £79, it is FROM £79; most fixed fee boiler repairs that I’m aware of ended up costing around the £300 mark.

Another bad catch is that there are a range of ‘exclusions’ that result in the heating engineer coming in the door, indicate the fault isn’t covered, and leave. Very little chance of a refund. Typical examples are: not safe to work on the boiler e.g. too high up on the wall or in the loft. A very common problem is sludge in the system, which does not qualify as a boiler fault and is therefore usually not covered. Again, ‘have a nice day’ and little chance of your money back. “Sorry, can’t get parts for this one” and “Incorrect installation, not covered” are also reasons I’ve heard from people a number of times.

Don’t get me wrong, there are cases where a fixed price boiler repair in south London is a genuinely good option, and I have even advised clients in the past to go that route. But there are a number of pitfalls, and now you know them, you can make a truly informed and intelligent decision.

Changes to guidance for landlord gas safety certificate inspections

In October 2013 the official guidance on gas safety around boiler repair and maintenance was updated by the HSE and one of the most significant changes is the section dealing with tenants and landlord gas safety certificate inspections. Although the actual laws governing gas boilers in domestic homes have not changed, the perception on how the legalities should be interpreted changes continuously, just like any other law. If it was all cut and dried, we wouldn’t need courts and lawyers; it would be simply a matter of identifying the transgression, look up in the table what the appropriate punishment is and hand it out.

It is not that simple. The ‘law’ on gas (the GSIUR is a statutory instrument so technically debatable whether it is actually a law or not) has not changed for 15 years, but the overall guidance document is now version 4. The official status of the guidance document is ‘advice’ but if you don’t follow the advice and something goes wrong, the engineer can expect a number of very uncomfortable questions. If those questions are not answered to full satisfaction, a court summons falling on the mat shortly after is not exactly a theoretical possibility.

One of the items that has changed drastically, is the ‘official’ view on which equipment needs to be treated in what way in rental properties. A landlord MUST have the gas-appliances of his let out property inspected every year; that in itself has never been disputed. What was unclear for a long time, is what exactly comes under the landlord’s responsibility and what not. Gas-pipes, oddly enough, DON’T have to be inspected for a lgsc as it is called. Flues and chimneys that are used by the gas-appliances on the other hand MUST be inspected. Gas-appliances MUST be inspected, too, with the exception of those that the ‘tenant is entitled to remove’. In general that means equipment owned by the tenant regardless of whether it is ‘fixed’ e.g. a cooker or fire on mains gas or ‘portable’ like a propane heater.

It is not uncommon for long term tenants to have a gas fire installed to supplement the boiler, sometimes for extra heat and sometimes just for the cosy flame effect. The tenant could remove these and therefore the landlord is not required to inspect them annually. The chimney can not be removed and for years it was viewed by many that therefore the landlord had to have the chimney of “the tenant’s fire” inspected and failure to do so was an automatic offence, but that has changed. The guidance now states unequivocally that if the boiler is part of the property as provided by the landlord and the tenant has a fire installed, it is NOT automatically an offence if the chimney is not inspected for the annual landlord gas safety certificate. It is still recommended that those chimneys and fires ARE inspected and for the little bit more money it would seem false economy not to, but it is now clearly only a recommendation and not an obligation.

Saving money on a south London gasbill

With gas prices at record levels and green politics bound to drive them up further, it is now at about every other boiler I repair in south London that people ask me what is most the most efficient way to use the controls. The question following that one is if it makes any difference. The latter is very easy to answer: yes, it can make a difference and possibly a rather large one at that.

The question on how to do it is a lot more complicated as it first of all depends on the system you have. If you have a cylinder, it is actually quite common that people achieve the opposite of what they have in mind when they turn the boiler down. If installed and set up correctly, the dhw cycle will shut itself down the moment the cylinder “is satisfied” and at that point the power use will become zero. If the boiler thermostat is turned down to below what is needed to click off the cylinder thermostat, the boiler will keep on cycling forever and keep wasting gas and electricity whilst doing that.

The other important difference is whether you have a conventional, or standard efficiency boiler or a condensing model. In the great scheme of things, turning down the boiler thermostat a bit on a non-condensing boiler is unlikely to save you much money. Personally, I tend to set them close to the maximum. With a condensing boiler, there is a fairly sharp cut off point above which the boiler will soon become noticeably less efficient. Even once you are below this critical point, the boiler will still increase in efficiency when the temperature is lowered further. Unfortunately, when the efficiency goes up, the efficacy suffers. This reduces the chances of giving useful, generalised advice even further. It’s not all bad news as there are two simple measures that are virtually infallible in helping you to save money and they are very easy to implement. Do what people did in the seventies: use common sense.

When it’s cold, don’t walk around in a tee-shirt. Allow for necessary ventilation but don’t leave doors and windows open.

Don’t have the timer on when it’s not needed. Depending on how well your house is insulated, you can turn the heating off half an hour to an hour before you go to bed without suffering hardship.

It is a bit of a challenge to give general advise that is entirely accurate all of the time but there are a few things where it is very hard to go wrong.

Lower the temperature on the room thermostat. Details vary depending on who you ask, but about 4% savings for each degree down is a common answer. Reduce the amount of hours you are heating; the shorter you’ve got your heating on, the lower your bill will be if the rest of the factors remain the same.

 Last but not least, the heating bill can be reduced significantly by fine-tuning the whole installation, the process of which is described on the webpage following this link; the info obviously applies to boilers outside south London just as well.


 The setting up of a central heating system properly requires apart from knowledge also skill and equipment. That means you are quite likely to achieve some improvement by upgrading your knowledge with the information found on the website, but in all likelihood you won’t be able to shave as much of your bill as I could.

Quote for new boiler install in southwest London

When I went out to repair a fairly dated boiler in southwest London this week, a 30 year old Potterton Netaheat, the owner told me that he was strongly considering to replace the boiler next summer. As the main heat exchanger had a 50/50 chance of being corroded, it seemed like a reasonable consideration. Apart from looking a bit tired, the boiler was also ‘kettling’. This is the term used by plumbers for a sound in a boiler that is identical to that made by a kettle when it is nearing boiling point. The sound is caused by uneven heat transfer which in itself can have two reasons. One is the build up of limescale, the other is corrosion that has eaten away the material of the cast-iron heat exchanger leaving a ‘pock-marked’ surface. The ‘holes’ in the material will get hotter than the flat surface parts and therefore cause the water inside to start boiling locally. The forming and collapsing of the vapour bubbles makes the characteristic sound.

He had several heating engineers in to quote him for a replacement and was rather bemused with the result. Four different people said they would come over to have a look. Two never showed up and of the two that did, one never gave a quote and the one that did quote had one look at the boiler, didn’t measure anything and asked a lot of money for doing very little. Needless to say he was not invited to do the job.

Since the owner was quite impressed that I not only showed up but also kept my promise that I would be able to get the boiler going again to keep him warm this winter, he asked if I could install a new boiler for him next year. He was a bit puzzled when I asked him the other chap had included a new gaspipe in his quote and admitted that he had no idea. Judging by the fact the current 30 kilowatt boiler was fed by a 15 mm pipe, it is unlikely the new boiler would meet the required spec without a new gaspipe for at least part of the distance. That seems to indicate that the “installer” was not operating legally, which in turn would have left the householder with an incorrect and illegally installed boiler. If nothing else, that would give the manufacturer of the boiler every reason to null and void the 7 year warranty the owner was very keen on getting.

The consequences of a boiler that is installed with a gassupply that is too small can run from anything like a voided warranty to a compulsory cut off at an inspection. The latter is fairly rare, but very inconvenient and costly if you are the exception to the rule.

This day and age, the old system of getting three quotes and taking the best one is not a very safe method any more. The vast majority of people I come across that are very happy with their tradesmen either got them by recommendation, or were able to verify their credentials in some way.

Gas cut off after boiler repair

When I went to a job this week where I was called in to repair a boiler that had been problems for a long time, I found a distressed home owner who had been put under undue pressure by a plumber. The boiler had developed a drip and the owner had taken the cover off to be able to stop the drip causing expensive damage to the printed circuit board aka pcb. The plumber (who had failed to find the cause of the problem) then set off on a sermon of fire and brimstone about how illegal it was what the man had done.

Much as I am in favour of gas safety, taking the cover of this modern boiler, where it had only a cosmetic function, was neither dangerous nor illegal. What is more, the often heard claim that diy on boilers is illegal, is not factually true. It may be really bad idea, but that doesn’t necessarily make it a crime. I see it as the 0.8 drink drive limit; as long as you stay under it, you are legal. Would I recommend aiming at 0.75 and then go drive around? No, I most certainly would not think that’s a good idea. Working on gas is very similar in the sense that it is illegal to do anything to a gasfitting that is dangerous. One of the very few things that is very clearly defined in this respect, is the difference between diy and ‘work’ as in: it’s professional. You are NOT allowed to do ANY work on a gasfitting that influences either the gas or ‘smoke/fumes’ which are defined as “products of combustion” or poc for short, unless you are a Registered Gas Installer if it is for profit/gain. This includes any and all forms of business, formal and informal, monetary payment, payment in kind, barter and even work for which you have not been paid, but expected to be paid in one way or the other. In every day, plain English layman’s terms: if it’s not your own boiler in your own home, it is highly unlikely that you can legally work on it.

Question: As the landlord, I own the boiler in the house I let out, can I do some maintenance or repair on it? Answer: No, end of.

Question: My tenant is pretty clever and very technical, is ok to let him sort out the boiler in return for a bit of money off the rent? Answer: Don’t even think about it.

Question: I barely break even on the house I rent out and the bloke in the pub that works for the gasboard offered to do it a lot cheaper on Saturday, is that ok? Answer: No, it most certainly is not, unless he has his own personal registration.

Question: I own my house and my boiler, can I replace the thermocouple myself? Answer: Only if you can do so safely AND have the equipment AND the knowledge AND the skill to carry out the legally required safety tests afterwards.

Question: The plumber claims that what I did is illegal and he is going to cut my gas off whether I like it or not, does he have the power to do that? Answer: No, he can do nothing without your permission. But……..

If what you did is indeed dangerous, he is legally obliged to report that to the Gas Transporter (often still called Transco, even though that is history), who can and will cut your gas off if that is what it takes to make the situation safe. If need be they can enter your house in an emergency WITHOUT a warrant, and the police WILL enforce that if really necessary. You would also be liable for all the costs, and we are talking serious money here. It may seem unfair, but that is the risk of doing diy on gas.

When does a landlord need a new CP12?

One of the subjects relating to landlord gas safety certificates that seems to remain a subject of much confusion and endless discussion is when i.e. what date do I need a new one. Although there are plenty of things that are not particularly transparent with regards to what most heating engineers still incorrectly call the ‘CP12‘, the WHEN is really simple as long as you don’t make a concerted effort to be difficult about it.

The LGSC is valid for a year, or as the GSIUR call it: a period of 12 months. No doubt a room full of lawyers could run up a £100,000 legal bill for arguing about what exactly constitutes 12 months. If number one was signed off on 12 April 2013 at noon exactly, must the next one be done before 12 April 2014 12.00 or 0.01?

I can understand the desire of landlords not to waste money on having the inspection done too early, but I think it is more time efficient to give somebody who is that worried a 10p discount rather than waste my time trying to figure out which is technically the correct answer.

As I tell my clients: my answers and explanations are intended to help you understand what is going on, not to win a high court case. Invariably, people agree it is more useful to understand 90% of plain English that may not be 100% legally accurate, then 10% of legalese that is totally correct gobbledygook. So plain English it is for the blog. If you want state contingent forward guidance that is guaranteed 100% correct for your particular tenanted house or flat that can be used to win a high court battle, than I can provide that, too. However, it will take a fair few hours to create and cost you a fair few bob.

Question: When do I need a CP12? Answer: The moment you rent out accommodation with a gas-installation of some kind.

Question: When does my tenanted house/flat need a landlord gas safety certificate? Answer: 12 months after the boiler is installed and from there on every 12 months.

Question: Does that mean I don’t need a new CP12 when I get a new boiler installed? Answer: That’s correct, you don’t need one for the first year after the boiler is installed.

Question: My tenants will leave 3 months after the inspection and the new tenants move in the next day, do I need a new cert? Answer: No, you do not need a new one until 12 months after it was done.

Question: I am a tenant and will rent a room out to help me pay the “bedroom tax”, will I need to get a landlord gas safety certificate of my own? Answer: No, provided the entire gas-installation is still the same as the day you move in, you do not. The purpose of the exercise is to make sure the gas-installation is safe, which has been assured by the inspection of the gas-installation done by your landlord.

An unusual repair on a Biasi combi boiler

Repairing another combi boiler in south London turned out to be a bit different than I expected. When you’ve been a heating engineer for years, you tend to have a fair idea what to look for by the time people have told you the make and model of the boiler, how old it is, the service history and what the complaints are.

The complaint here was that the boiler worked ‘fine’ as long as it stayed on but that it would lock out on a regular basis, and it happened more as the boiler got hotter. Other than that, there was no problem apart from 2 radiators not working. The boiler was a Biasi condensing model and installed by the previous owner of the house who happened to be a builder. Without tarring all builders with the same brush, I’ve seen quite a few who think they don’t need to waste their money paying a plumber to install central heating as they’ve seen it done often enough to be able to do it themselves. A popular tactic seems to be to pay a plumber only to do the gaswork on the boiler and then do the rest themselves. Typical problems to expect are wrong size pipe trouble, dirt, rust and debris in the system and generally poor quality materials and poor workmanship.

When I arrived at the job, this is what I expected and acted accordingly. Checked the radiators and found that they were not balanced at all but had all the valves fully open. This meant that the water going back to the boiler was about 15 degrees hotter than the boiler design ‘wanted’ and thus a likely cause for lock outs due to overheating. So I balanced the radiators which immediately resulted in the house heating up much more evenly and stopped the boiler from locking out at normal working temperature. But two radiators still didn’t warm a lot and when the boiler was turned up, it started to lock out again.

A closer inspection of the pipes to the radiators showed it was not exactly as it should be. The problematic radiators were in the extension and to make life easy, the “installer” had connected the additional pipes under the kitchen units with a self cutting connector t the main flow and return, and then six flexible tapconnectors, one after another. Tapconnectors are not heating pipes, but bits of rubber hose with metal braiding around them. Cheap ones can be restricted to about 4 millimetre inside compared to standard heating pipe which is 14 mm internally. Sure enough the small bore hoses turned out to be almost completely blocked by debris, rust and limescale which explained why they used to work but got worse and worse as time went by.

This is a good example of how “it used to work fine” does not mean that it was all correct before. If you have a Biasi boiler in south London and it has not been serviced and completely checked for a number of years, it may be a good idea to do it before it breaks down in the midst of winter.

My boiler is condemned after a CP12 Gas Safety Inspection

If there is anything that causes a panic under landlords and tenants alike, it’s the results and/or comments on a CP12, or landlord gas safety certificate as it should technically be called. It is a complex and confusing subject where changing a letter or a comma in a whole page of text can make the difference between heaven or hell. Today’s post is meant to alleviate the often needless anxiety in the form of a discussion, not to start suing people.

It is not unusual for me to get a phone call along the lines of:

“Can you do me a quote for a new boiler? I’ve got a rented property and the inspector has condemned it.”

In the vast majority of cases the house is not about to blow up, nor is the boiler beyond economic repair. When an annual gas safety inspection is carried out, you can have 4 outcomes. 2 of those are clear: perfectly ok, and ‘immediately dangerous’. Typical example of the latter would be a significant gas leak and fumes containing carbon monoxide spilling into the home. When that happens, the inspector only has 2 choices. He can either solve the problem there and then, or ‘make safe’. Making safe means either he caps off the gas (with permission), or refers the matter to the ESP, the Emergency Service Provider who will cap off the gas (with or without permission).

The 2 outcomes that are often not clear and in between 100% right and 100% wrong. They are Not to Current standards which is abbreviated to NCS or NtCS, and At Risk or AR. In politically incorrect plain English, the latter means unacceptable increase of risk for the heating engineer to simply ignore. It does NOT mean that your boiler is now suddenly unsafe. It usually means that it was not practicable to proof the boiler was safe or that due to certain imperfections, there is a higher risk of an incident than normal.

One of the most common reasons that we can not prove the boiler to be safe, is that the flue is boxed in. If we can not see for ourselves that the flue is in good condition as we are required to do, we have to treat it as a risk. In such a case, good practice indicates to advice the user that it is best to turn the boiler off and not use it until it has been possible to inspect the flue. It’s a recommendation, not an order. If the user feels it is too much hardship to follow that advice, they can turn the boiler on. But if something goes wrong, they can not turn around and say: “you should have done something”.

NCS/NtCS means just that: it’s not quite up to spec, but it does not pose an immediate risk either. Yes, it would be better to improve it, but it’s unlikely the house will blow up in the next hour or so if you don’t.

A difficult Potterton Suprima repair in south east London

One of the subjects that heating engineers can argue over til the cows come home without ever coming to a conclusion, is the use of modern, mostly digital equipment for boiler repair and maintenance. Some insist on using tools like flue gas analysers for every repair and every service whilst others only get them out when there is absolutely no other way of doing the job. Strangely enough, it doesn’t seem to matter much whether you do mostly service work in the heart of south London, or mainly repairs out in the country side, nor whether the guys are fresh out of plumbing school or nearing retirement.

As with many subjects, personally I think it depends more on the requirements of a particular job than that it is a matter of you should do this or it is always better to do that. A good example of this principle is in a Potterton Suprima boiler I repaired recently in south east London. The owner complained about irregular lock-outs that seemed to have absolutely no particular pattern. In case the term is not familiar to you, a (volatile) lock-out means that one of the boiler’s safety devices has detected a problem with a potential safety risk, and turned itself off. This can be caused by numerous different faults, from an interruption of the gas-supply, via overheating to an unsteady flame due to the burner being dirty.

The standard approach with intermittent lock-outs, is to have a quick look for anything obvious and if there isn’t something that stands out as the likely cause, you have no other option than to start at A and carry on to Z until you find the culprit. Using conventional tools, I did just that and found several things that were not quite right and corrected them. This made the boiler behave a lot better, but it would still fail if it was set to absolute maximum with a very low load. In this particular case, that was a 100,000 BTU or 30 odd kilowatt boiler running only the hot water cylinder that was nearly at the required temperature absorbing only an estimated 6 kilowatt or so. I could simply have advised to keep the boiler set at a three quarters for most of the year and only go to maximum in the midst of winter. I have worked on more Potterton Suprimas than I can remember, and I know that they should be able to run on maximum under any conditions, as long as the manufacturer’s instructions are fully met.

I had already established that all the sensors worked as required, the boiler was fully serviced and clean as whistle inside, and the input and working pressure were inside the prescribed tolerance. The odd thing was that where these two values normally move parallel, in this case one was slightly below the middle and the other slightly above. For some reason, this lead to the CO levels (Carbon Monoxide) to get near the maximum allowed when the boiler approached the very end of the temperature scale it was designed to work on. A minute adjustment of the burner-pressure lowered the Carbon Monoxide levels by about 80%, and the boiler stopped locking out.

The design of Potterton Suprimas is quite old and in those days flue gas analysers were quite rare, so the manufacturer does not give recommended guide lines for the CO and CO2 levels.


The measurements I found were inside general recommendations, so that in itself was no answer either. Only the fact that I knew from experience that the boiler normally can work without locking out at maximum, AND I would expect a lower CO level on this model, AND that conventional tests had shown the working conditions were met, led me to the solution. Most of my lobs are straight forward, but sometimes repairing boilers is really more art than science.

Landlord Gas Safety Certificates and gas-leaks

One of the most common misconceptions about what must be inspected for Landlord Gas Safety Certificate and what may be a good idea but not an obligation in south London, is testing for gasleaks. A LGSC does not include a compulsory Tightness Test, which is what this is called officially. You are now probably wondering if I at all know what I am on about and if this can be true. The answers are yes and yes; this is just another case where truth is stranger than fiction. I realist that to retain any credibility at all, I need to provide proof of something like this and so I will. The requirements of what a heating-engineer MUST do during an inspection, is specified in the GSIUR. A bit more about what that is exactly can be found on the page below and it also contains a link to a full copy of the latest update of the Gas Safety (Installation and Use) Regulations. The relevant sections are 36-3, 36-9 and 26-9.

HSE guidance document L56 about the application of gas safety legislation section 219 specifically states that although gas-pipes are not covered under the annual safety check, it is recommended that they are tested as well as visually inspected.

The odd thing is that not only most landlords and tenants think testing for gas-leaks would be compulsory, most gas installers think so as well even though they should know better. The reason for this misunderstanding of our obligation is probably as much to do with history as what seems to be just logical.

In the days that Corgi was in charge of the register of gas installers, they produced a pre-printed form complete with double carbon copy that was designed to cover all eventualities for domestic rentals. Almost all heating-engineers used this form and as it was produced by The Registrar, they assumed that you had to complete that form for a test. This, incidentally, also explains why so many people refer incorrectly to a Landlord Gas Safety Certificate as a CP12, which was the order code for the form that most people used and is commonly used as a sort of abbreviation.

That leaves the question when a test for gas-leaks actually is required. The answer to that one is simple: whenever a heating-engineer does any work that ‘opens the gas line’ and whenever he thinks he can smell gas or the tenant, landlord or responsible person tells us the can smell/have smelled gas.

Saving money on boiler repairs

Strange as it may sound, when the owner of a boiler that I repaired in south London decided to add a service to the work, he saved himself a lot of money. Not so much in an improved efficiency of the boiler, but by the lifting out of the burner that revealed a small water leak. Judging by the markings/stains, a tiny bit of water had been leaking onto the steel bottom of the combustion chamber. The combustion chamber is that part of the boiler that surrounds the burner and heatexchanger and make sure there is no risk of fumes including the highly toxic carbon monoxide to enter your home.

We all know, I presume, that steel frequent warm water dripping onto it will start to rust. This tiny leak that only caused the boiler to be needing to repressurised once a month, if that, would eventually have rotted a hole in the bottom of the boiler. Very few, if any, boiler manufacturers approve the patching of a hole in the boiler housing, which means the only way to repair the boiler is to take it off the wall. Once off the wall, you then have to take every single part from the old casing and build them onto a new one. On top of the high cost of a new casing, there will also be a lot of labour involved. Most of the time this means that when there is a hole in the boiler itself, even a small one, the boiler can not be repaired for less than a replacement would cost.

This case clearly demonstrates why it is a good idea to have a boiler serviced. It is not only a matter of proper maintenance improving reliability, it also reveals the beginning of small problems that turn into a major headache if left to fester. Waterleaks are only one example, soot build up is another common one, as are signs of arcing.

I know that nobody gets excited about boilers, unless they don’t work, of course, but whenever you have a heating engineer coming over for whatever kind of work, bolting on a service will usually cost you a lot less than spreading the cost by booking different visits for different jobs and those savings can add up nicely. For example, I normally charge around £65 for a ‘normal’ strip down service and a bout the same for a landlord gas safety certificate aka CP12. As repairing the boiler brought me over any way, adding a service and completing a lgsc could be done for half price because a lot of the work overlapped. That was an extra £65 saved for the owner on top of not losing the boiler in 2 or 3 years.

Finding a heating engineer for boiler repairs in south London

Earning a living by repairing boilers in south London, one meets all sorts of people; from about twenty to those that remember Henry VIII getting married (for the first time), from people with little formal education to nuclear physicists, English and those from places I hadn’t even heard about. Despite this wide diversity, there are some complaints I hear quite often, amongst which:

can’t find a plumber for love or money,

they (that’ll be me then) are too expensive,

I want to know what it costs, first.

There are quite a few more, but these are most frequent, so I thought I’ll give you the plumber’s view on them.

It seems odd that people can’t find a heating engineer to repair their boiler, especially seen from the fact that there are over 200 (yes, two hundred, it’s not a typo) in a 1-mile radius from where I live. Add to that the fact that most guys spend a lot more on advertising than they want, and there is clearly something odd going on. Some of the difficulty is due to the plumber and as you can’t influence that, I’ll ignore that and help you improve the bits you can influence. If a ‘normal’ plumber can be reached from about 8 til about 6, the boiler user has a statistical chance of over 50% (14/24) of things going wrong outside working hours. He (or she) is then bound to call between 7 and 9 in the morning. Not only will you have most competition from others, this will also be the time that the plumber is crawling his way through the infamous south London rush hour traffic chaos. I promise you that when we finally get to our first job of the day to see a customer who is in a rush to go to work himself, the last thing on our mind is checking voicemails or text messages to see who wanted us there an hour ago for a quote.

“What should I do?” I hear you ask.

Help me to help you, would be the answer. When you call, try to avoid the busiest time of the day. There are over 2000 different gasboilers in use at the moment, so it helps if you can give me an idea what I’m up against. Being able to tell me exactly which one you have e.g. it’s a combi boiler, made by Potterton, the model is a Puma and it’s the one with (or without) a pilot light more than doubles your chances of a useful answer than: “It’s quite old”.

Another thing that helps a lot, is doing some basic checks so I have an idea whether I should plan 30 minutes or 3 hours to sort it. This webpage helps you with that.


So now when you call me, it’s at a moment when I have a bit more time, and you can tell me the basics of what I need to know to get a rough idea of your problem. Your chances of getting an answer from me that you can actually do something with, are now about ten times better than calling somebody at random.

There is also an option for middle of the night, or any time of the day in fact: a quick to email to a href=”mailto:info@boiler-breakdown-repair-london.co.uk. I check often check my emails at night and in the morning before before I plan my route. All things being equal, this is probably the best method because not only will you get a quick response, I can also email you back with a proposal and my terms and conditions in writing so you know exactly what to expect when I get there.

Hi Ben,

We have a problem with our “boiler X, model Y, numer Z”, it suddenly stopped/gradually got worse since………. and it fails to ………….

We live at 12 Hight street, post code SE3 4CD. The boiler was here when we bought the house 5 years ago, but we do have all the manuals for it with the settings and technical details. You can reach us on the landline from 8-9.30 in the morning and from 18.30 til 22.00 in the evening; the number is 0208 123 4567. Alternatively, my mobile is 078910 123 456.

 Mr.&Mrs/John&Mary Jones.

What should a CP12 look like?

The most common misconception about landlord gas safety certificates that I have found in southeast London, is what it should look like. Especially letting agents and estate agents that need take care of the compulsory testing for their clients are prone to making comments like: “I’ve never seen a CP12 like this”, or “This is the wrong one, I must have on that looks like the others” when for some reason the inspection for the lgsc is done by another company than the one they are used to.

When the requirement for annual safety testing was introduced, the organisation overseeing the registration of competent gas installers was Corgi. To make life easy, they had a standardised from printed for which the order code was: CP12. It was very convenient for heating engineers because it could be used for any and all domestic gas appliances, covered every compulsory item, and came complete with two carbon copies; one for the engineer to keep, one that could be given to the tenant and the original for the landlord or his/her agent.

They may have been convenient, they most certainly were not cheap. Other companies started to make their own version of a from that could be used and for competition purposes (at least I presume that was the reason as I can’t find any other) these forms were just different enough to avoid copyright issues, but still looked very similar.

This was quite a while ago, in the days that most admin was done on paper. Today, most things are done by computer and something simple like a form like a LGSC can be done from every laptop, notebook and even from smartphones or Androids. There is not legal requirement for any specific form, and nothing stops an engineer to design his own template that has already got company details included. All you need to do then, is put the relevant details in the correct place, add the tenant’s details like name, address etc. plus those of the landlord/agent, click the button, and produce a complete printout which is neater than any handwritten form.

The layout of this template may be unrestricted, there is a number of items in addition to the details of the people involved that MUST be on there in order for it to be a valid Landlord Gas Safety Certificate.

  1. The date is required so anyone can verify that the valid period of 12 months has not expired.
  2. The location of all the items tested e.g. kitchen, living-room etc.
  3. A statement confirming that the tests comply with the legal requirements.
  4. All the relevant details of tenant, the landlord (or, if appropriate, the agent) and the engineer performing the tests.
  5. Defects found and what was done about them.

There is a number of other items that get routinely tested by most heating engineers, and are usually on the CP12, but they are not compulsory and therefore don’t have to be on the form, or do they have to be tested if they are on the form to make it valid.

Landlord gas safe certificates, what exactly is a CP12?

Over the years, I have done many a CP12 inspection in southeast London and was asked if I had to give the certificate to the tenants or to the landlords (or their representative e.g. the letting agent). The official wording can create some misunderstanding, but in real life the tenant will get a copy of the landlord gas safe certificate from the heating engineer there and then. Technically, the landlord gets the original lgsc, and then in turn is obliged to give the tenant a copy within 28 days on request. That means that if the inspector for whatever reason does not want to give the tenant a copy, he is NOT obliged to do so.

The certificate is not an approval, a pass, or a fail; it is a report from an engineer about his findings regarding the gas installation in that property on that day. It is not a forecast about how likely the system is to be reliable or efficient either. There may be comments and/or recommendations made on the form, but that does not necessarily mean the situation is unsafe and does not automatically require a boiler repair. If the engineer does find something unsafe, then he is duty-bound to inform the responsible person and advice on what to do. Landlords or their representatives are obliged to take action as soon as practicable to correct any defects found.

The wording in the legislation concerning gas is typical ‘legalese’ and not all that easy to read or understand to the letter if you are not involved regularly. That does not mean there is a whole lot that is optional. The bottom line is that the landlord is at all time responsible for gas safety in the rented property, unless it can be clearly demonstrated otherwise. Examples would be a precise contract with a letting agent where the responsibility is part of the agreement, or damage/alterations that are caused by the tenants or third parties. For those like myself who deal with gas safety on a daily basis, it is not that hard to spot the difference between ‘wear and tear’, a mishap, and somebody trying it on. The ‘trying on’ can be just as well done by an irresponsible landlord, as by a tenant attempting to hide that they damaged something, or encouraged by the never-ending reports about hefty compensation payments. Fortunately, these things are quite rare and in the vast majority of cases, an inspection is just routine.

To avoid giving people ideas I won’t go into details about the how and what, but spotting somebody trying to pull a fast one is about as easy as spotting the kid who helped himself to the chocolate and forgot to wipe his mouth.

What is included in a CP12 and who needs them

One of the questions about the CP12 that comes up regularly, is: who needs a landlord gas safety certificate? The easy answer would be that anyone who rents out residential accommodation containing any form of gas installation needs to have it inspected every year.

The obvious ones here are ‘real’ landlords i.e. council housing providers, housing associations and private landlords. Some less obvious examples of those that usually need a LGSC, are people that rent out bed-sits, rooms to lodgers and B&B owners.

If you rent out a static caravan or a boat that can be used as temporary or holiday accommodation, you most likely also need those certified. Although there is the odd exception, it is fair to say that in practical terms it is ALWAYS the responsibility of the owner of the accommodation to make sure the requirements are met. Failure to meet the obligations may be due to the failing of a letting or managing agent, but the onus is on the landlord to prove so. Landlords can not legally move the responsibility for this to their tenants, whether the tenants agree to it in the lease or not; it is still the landlord who needs the certificate.

The obligation is also virtually absolute, meaning that there are few if any excuses that are accepted when a landlord fails in his duty to obtain the necessary documents. Not being able to afford it, forgetting or not being able to find and available Registered Gas Installer are definitely bound to be dismissed. Blaming not having an inspection done on unhelpful tenants doesn’t have much chance of success either.

Some people think that the inspection for a CP12 is limited to gas appliances only, but this is not correct. In order for a boiler, water-heater or fire to work correctly, it is imperative that the ventilation and flueing are installed and working compliantly as laid out in the instruction supplied by the manufacturer of that specific appliance. A leaking flue or chimney is virtually always an undeniable reason for the boiler to be declared unsafe. Especially for older boilers of the open-flue variety severe lack of ventilation can also be very dangerous. A commonly found problem are closeable vents, also known as ‘hit and miss’ vents. For a landlord gas safety inspection, the ventilation is measured at the minimum possible setting. In other words: if a vent CAN be closed, it is considered to BE closed. In many cases, the situation has existed for many years and never been a problem. True as this may be, the inspecting gas installer has to look at what may happen in the future and must disregard that no problem has happened yet. This often upsets people, but it should be looked at as using seatbelts. The fact that you never have been thrown out of a car in a collision does not mean the belt won’t save your life at some point in the future. I don’t like wearing a belt, but I can see why we are forced to do it.

The duty of the landlord to have gas appliances inspected does not include those that are owned by the tenants and which they are entitled to remove.

The more technical side of the CP12 for a boiler

The next phase for the CP12 process to make sure boilers are working safely, is the part that requires more in depth knowledge of the gas side. Very similar to a car that starts, steers and stops, the fact that a boiler works at all does not mean it is working safely.

It is quite common to find one that produces far too much carbon monoxide or CO. Sometimes this is caused by a dirty burner causing ‘flame impingement’, but it could be a faulty gasvalve or a damaged/wrong injector, or the setting drifted out of range. The flame could be too hight resulting in it touching the heatexchanger. Another option is a problem with the fan not drawing enough fresh air in because it is worn or damaged. A dust/dirt build up in the airways can have the same result, and it could of course be a combination of the two.The most common way to verify this is with the use of a flue gas analyser or FGA.


Officially, it is called Electronic Combustion Performance Analyser, but I have never heard a boiler engineer actually using that term. Technically, if this test comes up with a reading below a certain value, a lot of boilers also pass the test to prove the minimum maintenance requirements have been met. This, of course, is a far cry away from having been serviced properly.

One of the compulsory tests that simply can not be omitted also comes under the “more technical side”. At all times during a landlord gas safety certificate inspection, we must verify that the amount of gas used is within the allowed range. This can be done by taking a reading of the gasmeter reading change during a defined period of time, or for some boilers by measuring the burner pressure. I prefer the system of reading the meter because in theory the burner pressure can be correct but the boiler input/output can still be wrong due to a faulty injector for example.

A test that definitely comes under ‘more technical’ but requires no particular tools, is checking the flame picture. This is more art then science as what you see needs to be regarded in the context of other findings rather than just judged by how it looks. I have seen flames that looked fine but still pumped out lethal amounts of carbonmonoxide and also flames that looked questionable, but were very clean.

This is where the skill and experience of a good heating engineer become obvious. It is know what to look for and how to interpret a set of symptoms and findings. When you do the tests needed for a CP12, the registered gas installer has a fairly large amount of leeway. This margin should be used with common sense and not in a rigid “this is always right” or “this is always wrong” manner.

Step 2 in the CP12 process

The second step in a cp12 process, is to go from the blatantly obvious to the “now you mention it, that makes sense” category. As I have mentioned before, I specialise in boiler repairs specifically in the south London/Bromley/Croydon/Kingston area, and therefore I use examples that I come across most: boilers. The principles remain the same though, as from a safety point of view there is not a whole lot of difference between a small boiler, a huge boiler like you find in large country homes, or another type of gas appliance like an open fire.

In the first part of the process we had established that the boiler actually works, there isn’t a gull nesting in the flue, and there are no gasleaks. Now there is nothing indicating an immediate danger to health or property, we look for imminent risks. A good one to begin with, is visually checking for stability. Is the boiler standing/hanging straight, or are one or more screws/bolts coming out of the wall? As a user or landlord you may not have given it a whole lot of attention, but you don’t have to go to plumbers’ school for years to work out what happens when the boiler moves causing the flue to leak when you think about it. Dito for the consequences of a boiler actually falling off the wall and breaking the gaspipe.

If all looks good with the boiler position, we look for “fiddles”, or in more official terms: improvised “repairs” or alterations. The gas equivalent of the repeatedly blowing fuse wire “repaired” by replacing it with a nail. Most boilers have safety devices that are designed to shut the boiler down when a dangerous condition occurs. Disabling such a safety switch by using a bit of wire to bypass it, or wedge it open, is NOT a good idea. It is also a dead give away that there is a very high likelihood of one or more serious problems with the installation. Doing something dangerous like this, also happens to be a criminal offense, but that’s a mere detail.

The dangers are not always on the boiler or flue itself, blocked or faulty ventilation is also fairly common and is as big a risk as an actual gasleak. Numerous times have I seen back boiler units in rooms where the ventilation openings had been blocked “against the draught”. Especially back boilers and “live” fires need large ventilation openings and as they tend to be in the sitting room, people find the cold wind coming from those vents unpleasant.

Understandable as the reaction to block them can be, it is a big mistake and a potentially lethal one. If the draught is really annoying you, get an experienced gas installer to change it. In most cases, it can be done in such a way that it is safe without being a nuisance.

Apart from the test for gasleaks, for which you need to know what to do and how to do it, covering the foundation of the landlord gas safety certificate inspection is very straight forward and not immensely complicated. If any of the points covered so far appears to be not quite right, don’t wait until it is time for the annual cp12, but get it looked at asap. Let’s face it, if you noticed a big bulge on the side of your car tyre, you wouldn’t wait until the next MOT to get it looked at, would you?

CP12 inspection start

HSE documentation L56 contains part of the guidance on domestic gas appliances, including boilers, repairs, maintenance and inspection. This indicates what should be done, whilst the GSIUR dictate what MUST be done for a cp12. Countless hours and hundreds if not thousands of pages have been filled about this subject without anyone ever having been able to write the definitive conclusion on what the best way is for a landlord gas safety certificate to be done. I won’t claim that the following is the perfect solution, but I have done it this way for many years in southeast London and never had a problem with it. Will it eliminate the threat of any party going to court over a dispute regarding the subject? Not really, but it will give all parties involved a pretty good level of safety, both technically and legally; that’s about as good as you will get.

The following is how I do it.

One thing I found out years ago to be a good thing to start with, is one of the last requirements of the standard safety tests as laid out in the legislation; verification of the correct working. This should be done after a boiler repair, after a service and for a landlord gas safety certificate inspection. It is not unusual for tenants not to quite know how the boiler works, and therefore not be aware of any defects. How do you verify the correct working? Simple, turn the heating on and see if the boiler fires up, turn the roomstat from high to low or vice versa to see if the controls work properly and then do the same for hot water. If anything fails to react correctly, there is not much point in carrying out an inspection as the installation is defective.

Presuming the boiler actually does work as it is supposed to do, this would be a good time to inspect the flue to make sure it functions safely disposing the fumes to the outdoor air. If a visual inspection shows the flue to be damaged, corroded or dangerously close to an opening that allows the fumes to get into a dwelling, you can stop right there as this would make it unsafe. It is not unheard of that boiler flues terminate unsafely, and I have personally found a number of occasions where building works had altered the flue outlet to indoors. The inspection stopped there and the installation made safe.

The next step is to make sure there are not gasleaks. This is, of course, provided that I didn’t smell any gas when entering the property, or people telling me that they have smelled gas. As with the flue, there is not much point checking the boiler for correct working if a gasleak needs repairing first.

Covering these three points may seem very simple and obvious, but you would be amazed at how many boiler engineers do a landlord gassafety certificate, without addressing these issues correctly.

Landlord gas safety certificate guidance changes

Testing for landlord gas safety certificates in south London has been relatively straight forward until this year, but that is about to change. At the moment, gas engineers have about half a dozen pages worth of guidance about how a boiler should be tested for a cp12. If current proposals are accepted and the documentation altered, virtually all this guidance will be abolished and the gas engineer will find himself working in a field where things have become very vague.

The following in this blog is not a prediction of what will happen, but meant as food for thought so interested parties including landlords, agents and engineers can prepare themselves for what is to come.

As we are still living and working in a recession, it stands to reason that a number of people will use the disappearance of the guidance to “improve” their competitive position. Heating engineers can do that by being less critical in their inspection and making it cheaper for the landlord or agent to use them compared to inspectors that apply a more rigorous testing. As long as the lgsc remains a purely administrative matter that has to be complied with, both parties are fairly safe. During the past decade or so, check ups on landlord’s inspections have been virtually non-existent.

The situation for all parties involved is very similar to drinking a little bit too much before getting behind the wheel: the real risk only becomes clear after you’ve had an accident. The situation is exactly the same when an incident happens with a gas installation of a rented property. The Gas Safe Register get involved, as do HSE and police including forensic teams. The landlord can expect a lot of questions about the maintenance dating back two years or more and the engineer should also free up a few hours to explain what he has been doing.

 There are several reasons why it is a bad idea to use the abolished guidance as a way to save a few bob. The most obvious one, is that it is ONLY the guidance that will go; the underlying legislation will remain virtually the same. Another one is that the amount of money saved by lax testing is extremely small compared to the costs if thing go wrong. The difference in price between the cheapest certificate I’ve ever seen and the most thorough one that includes a full service and helps to reduce cost of repairs, is less than £100 per year. In my humble opinion, cutting corners on servicing and/or landlord gas safety certificate inspecting is similar to not servicing your car: skipping a service once is probably not going to be a disaster, but doing it repeatedly is bound to cost you more in repairs than you save on neglecting the car.

Boiler repairs for CP12′s

Boiler repairs needed for a cp12 is another one of those subjects that are a never ending source of controversy. In today’s blog I do not pretend to give the answer to what is is right and what is wrong with all of it, but only attempt to shed some light on the general situation and help to avoid pointless and costly disputes.

All too often the question comes up whether or not a certain repair is necessary in order to obtain a valid landlord gas safety certificate. Looking at the literal text of the gas legislation, the answer is that in and of itself, no boiler faults have to be repaired to make a cp12 “valid”. This is because the lgsc is only a means to an end; the end being the verification that a gas-installation is maintained to a safe standard as required by the GSIUR. Therefore, if the inspection reveals a defective flue, it is up to the landlord to make sure that repair is carried out. The cp12 proves he (for reasons of simplicity, I am not politically correct in these blogs and refer to anyone as “he”) met his obligation to inspect the situation and can then meet his obligation to maintain safety by instructing somebody to repair the boiler. Sometimes it is practical to have the inspecting engineer do the work and at other times it will be somebody else. A typical example for keeping the jobs separate, is that the inspection is done by somebody who is very good at spotting problems and has all the equipment for inspections that help to minimise the disruption for tenants. He spots a difficult problem with a flue, which is then sorted out by someone who specialises in repairing difficult flue problems and has all the specialist equipment needed for that particular specialty.

A textbook example of an issue that becomes a dispute, is when a fanned flue boiler has been installed in a way that is not quite up to spec. Using a hypothetical 10 year old, non-condensing boiler that has been inspected 8 times and always found to be in perfect working order. Upon its 10th anniversary inspection, the same boiler that was absolutely fine for the past 3649 days (I’ve allowed the extra leap year days for tolerance) and now, whilst nothing has changed and nothing is damaged, worn or loose, the inspector declares the installation to be Immediately Dangerous, and claims the boiler has to disconnected from the gas-supply. I don’t blame people for thinking this has to be a con, but it can actually be totally correct. How?

(Here are some of the most common cons for boiler repairs in south London that I have come across)


A common distance required by the manufacturer for the flue to be away from a door or window, is 300 mm. If this distance is not met, say it is only 250 mm, the inspector must make doubly sure that there are no fumes entering the house. This is obviously by how much wind there is and from which direction. That is why it is perfectly possible that during the previous 8 CP12 inspections all was fine, and suddenly after 10 years fumes are blown into the property. That makes it a no-discussion case of an Immediately Dangerous installation. This then leaves the inspector no alternative than to recommend the boiler is made safe and until such time be disconnected from the gas supply.

This is by no means the only case of where a boiler repair is deemed necessary after a landlord gas safety inspection, there are countless other scenarios.

Landlord gassafety certificates aka CP12 and the different categories of findings

Today’s boiler repair blog is about the most common misunderstanding about landlord gas safety certificates, which is that it “passes” or “fails”; it does not. A CP12, as it is often referred to, is a summary of the opinion formed by the heating engineer’s inspection of the boiler and gas-supply. Part of this opinion is a recommendation for what to do about anything that is not 100%. It is then up to the landlord to decide whether or not to repair the boiler.

There are four different “classifications” for each item inspected.

In an ideal world, the inspector finds everything to be completely fine, so I will call that option 1.

More common is to find one or more things that are not perfect, but not dangerous either. An example would be a SLIGHTLY under-sized gas-pipe; it would not quite meet the requirements, but it has no negative effect on the working of the boiler. Something like this would be qualified as Not to Current Standards, or NtCS for short.

This should be mentioned to the landlord, but no action is required.

Partly due to Health and Safety requirements being tightened up on a regular basis, “slight” faults become “medium” problems. They are called At Risk or AR for short. It means that there is something that is not right without posing an immediate danger, but has a distinct risk of becoming dangerous if nothing is done about it.

It should be mentioned to the landlord that action is needed, although it is not compulsory at this moment. It is recommended that the engineer advices the user to turn the boiler off until the boiler is repaired. A typical example of this would be a FiV which stands for Flue in Void.

The last option is where things are really wrong and something poses a realistic danger to health, life or property if the use is continued. This situation is known as Immediately Dangerous which is abbreviated to ID. An obvious example of an Immediately Dangerous situation, is a significant gasleak. The engineer is not allowed to simply walk away from this kind of problem, and has 3 options.

  1. Repair the boiler there and then.
  2. Disconnect the gas-supply if the user permits it.
  3. If the disconnection is not possible for technical reasons or because the user or landlord denies permission to disconnect or repair, the engineer MUST contact the Emergency Service Provider and report the details of the dangerous situation. The ESP will come out in a matter of hours and WILL disconnect the gas. They either do that by implementing their Right of Entry (they do NOT need a warrant) or by digging up the road and cutting the supply in that way. The ESP in south London is National Grid, Southern Gas Networks, or one of the approved contractors.

 This blog about CP12s and boiler repairs is intended solely for information to gas users, written in layman’s terms for the purpose of increased understanding and avoiding problems, not to challenge anybody. It is unbiased and without prejudice.

Landlord gas safety certificates for boilers and the Flue in Void

Of all issues that plague landlords that need a landlord gas safe certificate in south London, the FIV, short for “Flue in Void” is probably the one that has caused most problems. There are various reasons for this, the most obvious of which are:

  1. It is a new problem in the sense that before 2013 it was no problem if an existing flue could not be seen over its entire length.
  2. A large number of landlords are still not aware of this new issue and those that do know about it, don’t know exactly what should be done.
  3. Most Registered Gas Installers are unsure of what is allowed and what not. As a result of this, landlords are bound to get different opinions when they ask different engineers for advice.

 I am currently in the process of dedicating an entire webpage to the subject of the Flue in Void issue and the problems it can cause especially for landlords, so you may want to come back to this blog soon for the link to more information on the subject of FiVs.

In the meantime, after studying the subject and verifying details with those that are dealing with it on behalf of the Health and Safety Executive, I have summarised what seems to be the current consensus and am publishing it as much as possible in plain English. As such, this should be seen as an informed opinion which is without prejudice and not written in stone.

One of the simple questions is which flues come under this new guidance: ALL that can not be seen over their entire length. The part that goes through the wall is exempt from the requirement to be able to see it.Another simple one is: what is an engineer who works on the boiler or does an inspection supposed to do when he finds a situation where he can not see the fluepipe for whatever reason?

He is required to advice you that the boiler is considered unsafe to use and should not be used until the flue can be verified as safe. He should then ask the responsible person for the property for permission to turn the boiler off and do so if permission is given.

A heating engineer, registered gas installer, plumber or whatever you want to call them, is not obliged to turn the boiler off or disconnect the gas purely on the basis of not being able to see the entire flue, nor does he have the power to do so if the responsible person for the property refuses to give permission.

However, if you refuse to turn the boiler off and keep using it, you are likely to find yourself in serious trouble if something goes wrong. If the flue were to leak and somebody, whether tenant, visitor or any third party, suffers ill effects from Carbon Monoxide inhalation, you can be charged with a number of offenses and also find yourself being sued for compensation. Both the criminal and civil litigation will have a good chance of succeeding and turn out to be very costly for you.

As stated in the first blog about landlord certificates, this is not written to help you base a legal challenge but to avoid lengthy and costly disagreements in the southeast London area and is without prejudice.

Saving money with a lgsc

Due to my specialisation in repairing boilers in the south London area, the requests I get to carry out a landlord gas safety certificate inspection come from people who are looking for an expert boiler engineer who can also help them out with this legal requirement. This is a very different angle than that of a landlord who is looking for whoever can get him (or her, of course) this piece of paper the quickest or the cheapest.

Many a landlord wants a lgsc as cheap as possible with as little hassle as possible because they see it as just another pointless cost to their business. Although this is perfectly understandable, it is not necessarily always correct.

Part of the cost charged by a heating engineer to produce the certificate, is the same as for a service: travel time and compulsory checks. I tend to charge roughly the same for a lgsc as I charge for a full stripdown service if done separately, but when done together I take about 70% off the price of the certificate because it takes so much less time. As such, adding a service to an inspection gives the landlord much better value for money.

But the best value from adding the service, comes from spotting small problems before they become big ones. The best example is the tiny leak. Every so often I come across a tiny leak that drips on what is known as the “combustion chamber”. This is the area where the burner is housed, usually together with the fan and sometimes the gasvalve. It is invariably a small, quick and easy repair on most boilers, say between £50 and £100, sometimes even less.

How can spending £100 save you money? Very simple. On almost every boiler in use in this country, a small drip will rot a hole after 2-3 years and that almost always means a new boiler. Depending on size, place, and how much of the peripherals need doing too, a good new boiler will in most cases set you back at least £1500, often more. That is one expensive little drip. There is a number of similar “hidden” faults that become evident with a full service, but almost surely remain hidden until it is too late and they have become expensive.

Now there is service and service. In most cases, the heating engineer has technically/legally “done a service” if some electronic measurement show that the boiler is operating within certain set parameters. Although there is nothing wrong with doing this what I call “small” service, they don’t reveal anything about beginning problems but only about faults that have moved the boiler outside what is safe. Therefore, it is not likely to save you money in the long run having only small services done.

Full services also known as stripdown services will also make it much more likely the boiler passes next year’s inspection without too many problems.

As stated in the first blog about landlord certificates, this is not written to help you base a legal challenge but to avoid lengthy and costly disagreements and is without prejudice

The purpose of a landlord gas safety certificate aka cp12

The purpose of a landlord gas safety certificate, also (incorrectly) known as a cp12, is to prove that the gas installation of a rented property meets the minimum safety requirements at the day of the test, very similar to a car MOT. It says nothing about the quality or reliability of the system, nor does it guarantee that a boiler that is safe today will still be safe 5 months from now.

The compulsory technical elements tested are:

  1. Are the Products of Combustion safely removed to outside the dwelling?
  2. Is there sufficient supply of fresh air to guarantee correct combustion and cooling of the boiler? This part is rather archaic as almost all boilers these days are sealed units that get their air through a purpose built duct directly from the outside. However, for the few that still do get their air from inside, this is a very important aspect.
  3. Measuring the amount of gas used to ensure the boiler is operating inside the limits is was designed to work. A boiler that works outside those limits is at a significant risk of not working safely.
  4. The correct working of the boiler to make sure it is safe to use.

A detail that surprises most people, is that a search for gasleaks is not compulsory if nobody mentions a smell of gas. Although a safety inspection in itself does not call for a gasleak test, it would be rather hard to explain if a gasleak as found shortly after an inspection, so most RGI’s will do such a test.

Registered Gas Installers have a legal duty of care and are by default compelled to carry out certain basic checks after inspecting or working on a boiler. When we inspect a boiler that is found to be fine on the aforementioned 4 points but has lost all but one of the screws holding it in place and is in realistic danger of falling of the wall sooner rather than later and thus is at risk of causing a serious danger before long, we have no other choice than either repair that defect or condemn the boiler.

There are a number of other situations that will force us to take action.

1. Significant damage or corrosion to boiler, flue or gaspipe.

2. Lack of means to shut off the gas supply in an emergency.

3. Changes in the flue or building work near the flue that can cause fumes to come inside.

As stated, there are defined minimum tests that must be carried out for ALL lgsc inspections, but is the boiler engineer’s responsibility to make sure the installation is safe. This means we are compelled to test, measure and verify whatever it takes to guarantee the installation is safe and can not claim we did the inspection correctly if it turns out there is an incident caused by an obvious defect purely because we only did what was compulsory in all cases.

Landlord Gas Safety Certificates explained

One of the subjects to do with boiler repair and maintenance that is a never ending source of confusion, is Landlord Gas Safety Certificates. Even within the gas industry, there is a lot of confusion about what it is, why it is, when it needs doing and what needs doing. In the following few blogs I will shed some light on the how, what, when and why. This blog is written to help landlords, engineers and tenants understand what is required and what not and thereby avoid lengthy and costly disagreements that end up wasting people’s time and money in court. As most people do not have a law degree, this is written in every day straight forward English instead of “legalese”. It is therefore not 100% legally airtight and a lawyer could poke holes in it; this is not written to help you base a legal challenge, it does not take the side of the landlord, tenant or engineer and is without prejudice.

As I specialise in the repair and maintenance of boilers, I will use the word “boiler” rather than the more correct term “any gas appliance designed for the use of mains gas of which the primary constituent is methane supplied by National Grid at a nominal pressure of 21 millibar in Great Britain or Ireland”. If you can not come up with a likely reason why I made this choice, you may want to stop reading here and watch re-runs of Teletubbies instead.

A good start is to define what the difference is between a LGSC as it is called in short, a service and a repair. A LGSC is a certificate that is issued after the inspection of a gas installation in a rented property. Contrary to common belief, it does NOT include a service, nor any other form of maintenance, nor does it tell you anything about how good or reliable the boiler is, and it does NOT pass or fail the installation. In short, the report checks a number of safety related issues and states whether those items meet the required minimum criteria.

English law requires the landlord of any rented property to get this certificate no later than 12 months after the issue of the last one. Although there is a legal requirement to maintain a boiler to a safe standard, there is NO legal requirement to service the boiler at the time of the inspection.

Servicing can be done at any time and the law does not specify when or how often. Some boilers need maintenance every month, others can run perfectly fine for 3 or 4 years without the need for so much as taking the cover off.


Although slightly out of scope of the subject, it does help to have a rough idea of where a service stops and the work turns into a repair.  For me, a standard service does not go beyond cleaning, lubricating, measuring testing and correcting things like pressures, flows and such in the boiler. If a leak is discovered in or near the boiler, than that is a repair if it is not solved by cleaning, tightening or lubricating. A radiator that doesn’t get warm is not part of a service, nor are rattling pipes, timers that don’t work or taps that give poor hot water.

Potterton Puma repair in southeast London

During the repair of a Potterton Puma combi boiler recently in Dulwich, I was again surprised at how well this model keeps up despite not being treated as they should. This part of southeast London has a great number of these that are still chugging along and with a bit of maintenance should continue to do so for several more years.

I have heard many a plumber, or heating engineer if you prefer, that they are no good and not worth repairing. I would beg to differ and so do my clients that still have one of them. More often than not when a Potterton Puma fails to do its job, it is due to reasons that are actually not really boiler faults.

In this particular case, it was due to a blockage of a safety device. Dirt/corrosion/limescale in the system had completely closed the “entrance” of the sensor. As a result, it did not register sufficient pressure to work safely triggering the safety that prevents the boiler from destroying itself.

The installation instructions clearly state how the boiler should have been installed, and what should be done to prevent the system from rust damage. When those instruction are ignored by the installer, you can’t blame the boiler for packing up. If the manufacturer of a car prescribes an oil change twice a year but the owner keeps driving it on the same oil that was put in from new, you can’t expect the car to keep going without problems, can you?

As it is such a popular boiler, I have dedicated a whole page to it.


Despite rumours to the contrary, virtually all parts for these boilers are still quite easily available and so far I have never had to disappoint any of its owners. To date, my successrate on these workhorses is 100%.

I am not saying it is the best boiler ever made, but it certainly is not the worst. If you have one, and are hoping to keep it for a few more years, I highly recommend making sure the system is clean and free from sludge. Once that is done, you can rely on a Potterton Puma as much as the next one.

Broag Avanta Remeha repair in Brockley south east London

As described on my page that is dedicated to Broag Avanta Remeha repairs, they are a bit different.


One of the more difficult jobs I have done in the past few years, and easily the hardest one this year, was not so long ago in south east London on the Ladywell and Brockley border. For starters, it was not a consistent fault, but one of those “sometimes, sometimes not” cases. That usually means that when I am there, it works fine and about 3 minutes after I come home I get a call that it stopped again.

The only thing you can do in a situation like that, is start at the beginning and work your way through to the end. It is a bit of a long winded process, but it tends to bring the solution for awkward problems.

First step is to see if everything is connected properly with the right kind of pipe and no obstructions anywhere. This particular Avanta Remeha was the combi version, and the biggest model at that. Nothing is guaranteed in this life, but in general it is more likely that the installer cut some corners when you find the smallest models of a range. This one seemed to confirm the rule, and it all looked pretty decent. The boiler sat nice and square on the wall, flue was correctly sealed where it went through the wall, gaspipe was sufficiently large and all the pipework was straight and neatly soldered. We all know you should judge a book by the cover, but if it all looks like good workmanship, it usually is.

The next steps are to check if the electrical supply is correct and the system clean. It proved to be the case too here.

With all that verified, and the controls with a combi being all inside the boiler apart from the roomthermostat, it is now proven that the boiler itself is at fault. These boilers, like virtually all combis, have a pressure gauge that tells you if there is enough water in the system. When you run the central heating for a few minutes, the rising temperature causes the pressure to go up which in turn proves the gauge is working. So far, so good; now turn the boiler to maximum output, and a quick test on the meter to see who much gas is used. This is the easy check to see that the boiler is running at the rate it was designed to work at. By doing this, you can also tell whether or not the gasmeter is functioning correctly.

With all the “rough” work out of the way, it is time for the more intricate parts of boiler repair diagnosis. Time to get the flue gas analyser out and to get a grip on the CO2 and CO levels at minimum and maximum output. They had only drifted a tiny little bit since the service last year, so this was unlikely to be the problem. After they were both re-tuned to exactly what the book says, the fault still persisted as I expected. By removing, measuring and verifying as much as I could, it turned out that there were 4 parts that were not quite as they should be, but not really broken either. Luckily, the parts for Avanta Remehas are not hugely expensive, so the repair was still quite affordable.

Saving money on boiler repairs

Saving money on your boiler’s service and repair bills in these times of rising costs and decreasing incomes, is far more important than at any time during the past decade. The question of course is: how?

There are a number of things you can do to achieve this in real terms.





Strange as it may sound, you can select not only who you pay your money to, but also what on, and when.

Most of my clients, and presumably most people in the whole country, have more experience with cars than with boilers. I have found that when I translate boiler principles into car related issues, suddenly almost everybody understands straight away what at first was a mystery. Let’s try that here.

How can you select where and how (much) you pay for boiler repairs?

Step one. Separate the ideal world from planet earth, and accept that at some point your boiler is likely to break down. With that in mind, it makes sense to find a reliable plumber when you’ve got the time to look around and check him out before you need him in a hurry.

Step two. Cars benefit from servicing and so do boilers. Save £30 by not paying for clean oil will sooner or later end up with a £3000 bill for a new engine. Just like with a car, a boiler is unlikely to die from skipping a service, but the longer you neglect it, the higher the chances are that it will break down. I have found a great car mechanic who does an excellent job for around £40 per hour. When I broke down several years ago and had to pay for a tow, it cost me twice that per half hour.

Step three. You can’t plan when your boiler breaks down, but you can plan your services and non-urgent repairs. A small leak should be sorted out before it becomes a big leak. In most cases, something like that can wait until spring/summer when plumbers are less busy. After summer when the heating comes on for the first time in months, we are busy beyond believe. That tapers off a bit after a month, but our life gets even more hectic the first time temperatures drop below minus 2. During those months, I come home anywhere between 7 and 9 at night. Anyone who promises discounts or cheap repairs, is bound to be either a liar or not very good at repairing central heating problems.

Step 4. Selecting who you pay can be done quite easily. You can ask anyone you know for recommendations. In today’s world, that can be done face to face, or online. The problem with online is that you don’t know how reliable the “voice on the other end” is. But what you do know, is that nobody is perfect. When I do my own research, and find a company that has 47 five-star ratings, I get suspicious. Nobody can make 100% of their customers 100% happy for 100% of the time; it is simply impossible. To me, that means this company is happy to put up fake references. It seems logical that if they are happy to lie about their customers, they will be happy to lie to me about the quality and/or price of what I am planning to buy.

Nothing is 100% safe, but a black and white guarantee of no charge if I can’t find the fault is probably the next best thing. Dedicating a page to telling you the most common cons that are used by plumbers, should help a bit too.

And last but not least, you can ask questions about specific examples on the blog, and by email. The only thing I can’t do, is make the choice which heating engineer to call for a boiler repair; that is your job.

Potterton Performa repair in SE21, Dulwich south east London

During a Potterton Performa repair in SE21, Dulwich, south east London recently, I was once again reminded of many times seemingly unrelated install flaws go hand in hand with boiler problems. In this particular case, the heating would sometimes work, sometimes come on but go off too soon, or not work at all. The hot water was the same; one day you could run a piping hot bath and the next day you would get frozen as halfway through a shower the water would turn cold. This particular Potterton Performa, was the combi model of the first series that was not condensing; They are quite popular in Dulwich SE21.

Due to the way combination boilers are designed, the fact that the fault appeared both in central heating and hot water mode rules out a lot of possible sources that cause the problem. Going through the standard tests to assure that all the basics are covered was the next step. The pressure gauge stood above 1, so that could not be it. Quick top up to verify that the gauge wasn’t stuck on 1 whilst in reality the pressure was too low. The needle moved, so that was fine.

Several control lights were on, which proved that the electricity was present. It may seem obvious, but lots of people are not technical at all and either would not think of checking the fuse, or simply not know how to do it. The owner conveniently had a gas hob, which produced a nice blue flame for a couple of minutes without any fluctuation. Great, that pretty much rules out a problem with the gas supply.

On the page dedicated to this model, I called the Potterton Performa a workhorse.


The reason I used that description, is because this boiler is not particularly spectacular. It doesn’t have many options, doesn’t have many choices, it just sits there, doing it’s job.

Nevertheless, this one didn’t really want to play ball. Having the shower halfway through turning cold on you is not funny and can’t be easily mistaken, so I presumed the owner had told me fairly accurately what the problem was. Sure enough, when I was there the boiler came on immediately and warmed up nicely. Finally, after turning the boiler on and off in various way for heating and hot water, it cut out. From the way it did it, I could prove that the fault was in the electronics; it needed a new printed circuit board or pcb for short. From the way the problem was described, the board was the first suspect. The problem with a suspect pcb, is that it is the favourite excuse from guys that don’t quite know what they are doing as well as the number one for con artists that try to whack up the price. A pcb fault is hard to prove or disprove, and they tend to be costly, and the Potterton Performa is no exception to that rule. What I found interesting, is that this was another example of a poorly installed boiler that went wrong whilst they are normally quite reliable. There is no logical explanation why a pcb would go wrong due to poor quality installation. A bad job, usually means sloppy cables, pipes to small and going all over the place, dirt, rust and muck in the boiler and radiators and so on. All this has seemingly nothing to do with the electronics inside the boiler. However, Potterton Performas that I have repaired, were far more often showing proof of poor quality workmanship during the install, than what I would qualify as a neat job.

It makes you wonder. Looking at it from a maintenance side, people SE21, Dulwich call me in for a servicing as well, in stead of a repair. Those that clearly had the job done by a conscientious installer and everything looked neat and tidy, invariably told me that their Potterton Performa was perfectly reliable.

The difference between positive pressure boilers and negative pressure boilers

Room sealed boilers come in three variations when you classify them by flue type; balanced flue, positive pressure and negative pressure.

The balanced flue type is the easiest to recognize. It is has a great big rectangular grill sticking out the wall. They tend to be about a foot high, eight to ten inches wide and about three inches deep. If they are at ground level, officially anything under two metres, they need a protective guard around them as they can get pretty hot. It looks like, and is almost the size of, a metal shopping basket.

The other two look the same from the outside. The most common form, I would say covering over 95% is a 100 mm or 4 inches pipe with some sort of other pipe usually in the middle. It can look slightly different with the second pipe against the inside top of the outer pipe. Some boilers have some sort of diffuser so you can’t actually see the inner pipe.

The important difference between a boiler working on positive pressure and negative pressure, can only be seen inside the boiler. As incorrectly closing the boiler can be very dangerous, you must NOT open your boiler to find out. Nor should you open it for any other reason.

Some older boilers, the Potterton Netaheat is probably the most famous of them, had a positive pressure case. The boilers are designed in such a way, that the fan sucks air from the outside into the boiler, creating the positive pressure. This air will naturally flow to the burner area, and after reacting with the gas during the combustion, been blown outside.

Because the boiler case, which is in this case the combustion chamber as well, is under pressure, any damage to it can lead to the escape of toxic gasses including carbon monoxide. The same goes if the boiler is opened, and then not closed in the correct way, or if the seal is damaged. Sometimes, when the boiler ignites a bit slowly, the build up of gas mixture in the boiler can cause a miniature explosion. Nothing in itself to worry about, but it can distort the cover slightly. Repeat this dozens of times over the years, and you can have a very dangerous situation without anyone realising it. This is one of the main reasons why this type of boiler should be serviced every year.

The Potterton Netaheat was followed by the Netaheat Profile, which shortly after it’s launch was renamed simply Potterton Profile. It was very similar in design to the Potteron Netaheat, only the fan system was changed in such a way that it became negative pressure. Since then, virtually no boilers have been made with positive pressure cases. More detailed information about these particular 2 boilers can be found here.


Negative pressures boilers have the fan directly connected to the flue. This way, the pressure inside the boiler is a fraction lower than the “outside” pressure, which makes them inherently safe for leaking carbon monoxide and other harmful products of combustion.

Getting the right radiator

Getting the right radiator is as important as getting the right boiler. If the boiler has insufficient capacity, all the radiators in the world will not keep the house warm. Reversely, a massive boiler won’t do a lot of good if the rooms don’t have the right radiator.

There are various types of radiators that each have their use. The “normal radiator comes in essence in four different models. The most basic one, is a panel radiator without “fins”. I haven’t seen any of those in the shops for a long time, the ones I’ve seen in people’s homes were always quite old.

The two most common models used over the past decade, are what are known as “singles” and “double” radiators. Singles, are a radiator panel, the bit that you see, with fins attached to the rear of them. Doubles are essentially two singles, attached back to back. In other words, two panels, with two sets of fins between them. They are therefore a bit thicker than singles, but have virtually twice the output of a single for the same height and width.

The “vertical” radiators are becoming more popular these days. They look more stylish, and require much less horizontal wallspace. This allows the installation of a radiator with a fair amount of output in “lost” corners.

Another model radiator that is becoming more popular, is the column type. They have roughly the same output as normal panel radiators, 2 column models are comparable with singles and the 4 column type is similar in output to a double. No real technical advantage, but they do look nicer than standard rads.

Towel rails, also known as towel ladders, have been on the increase for years in bathrooms and sometimes in kitchens. They obviously keep towels nice and warm, but have a relatively low output for their size. The towels hanging over them reduce the airflow past them, which reduces the capacity to heat the room they are in, even further. It is very hard to oversize a towel rail. A white one of 1800 by 600, or 6 by 2 foot in old money, has roughly the same output as 600 by 600 panel radiator, and that is provided there are not towels draped over it. Chrome models have even less output that white ones; between 20 and 30% less. In general, err on the side of bigger is better with these if you want to get the right radiator for the bathroom.

Getting the right boiler

Getting the right boiler is probably the most discussed subject on any forum to do with central heating and boiler in any form. I’d say it is bound to stay the most favourite subject for some time due to a number of reasons. One of those is that it is for a large part due to personal preference. On top of that, it is a typical case of: it all depends on your personal circumstances. People try to design “rules” that would dictate or prove that a certain choice is best, but like in most situations, it simply doesn’t work.

In essence, there are three different types of boilers and each have advantages and disadvantages. Getting the right boiler is therefore likely to remain a matter of compromising. The three different types of domestic gas fired boiler are the combiboiler, the system boiler, and the open vent boiler.

The combiboiler has several advantages over the other models. There is no need to program a hot water production cycle because this type has the capacity to produce hot water immediately. This creates a second advantage in the form of unlimited amounts as there is not storage facility to run out. The downsides are that the amount of hot water available at any time, is limited to the capacity of the boiler. Therefore, only large capacity combis can run two showers at the same time, and more than that is simply not possible. For houses where more than two bathrooms are likely to be used simultaneously, the combi is not a good choice. The second disadvantage, is the need for mains water supply of significant flow and pressure. If either is on the low side, a combination boiler may not work properly. If the mains pressure supplied by the water company is low, very little can be done and an open vent system with storage tanks will be a better solution. Where the supplied mains pressure is sufficient, but the incoming mains pipe is small, it can be upgraded to increase the flow capacity.

A system boiler uses a hot water storage unit, usually called “the cylinder”. An unvented cylinder used for hot water production, can supply large amounts of hot water. This type of installation gives great performance when there are more than two bathrooms likely to be used at the same time. The downside is that the hot water supply is limited to the size of the storage capacity. Once this is used up, there will be no hot water until the boiler has heated the cylinder up again. The other downside, is that the performance also depends on the flow and pressure supplied by the incoming mains water. Just like the combi boiler, this system is not reliable if the supplied mains pressure is low.

The unvented boiler with cold water storage tanks (usually located in the loft) is not reliant on mains pressure, and is the common solution for getting the right boiler where mains pressure is limited. The downside here, is that the storage tanks are open to the atmosphere, and therefore needs measures to prevent unacceptable bacteria growth, especially in summer.

Heating with a boiler versus using a fire

People ask me about using gas fires in combination with central heating on a regular basis. Without looking at the technical details, it seems to make sense not to use a boiler if you only need a little bit of heat to get the cold out of the room. The problem is that most fires are much less efficient than boilers. Especially the nice looking ones that imitate a wood burner or have a coal effect, have two major disadvantages. First of all, unlike modern boilers, they tend to need hefty ventilation. The default opening is 100 square centimetres, which translates to a hole of roughly four by four inches. This opening must be directly to the outside, and may not have a shutter of any kind. In combination with the chimney that creates a natural pull due to it’s construction, you now have significant draught that loses you a considerable amount of heat all year round. But that is not all. The high efficiency or condensing boilers that have been compulsory since 2005, are generally between 88 and 91 per cent efficient. The “normal” boiler that were commonly installed between say 1980 and 2005 vary a bit more, but are still mostly between 70 and 80 per cent efficient. Most of the decorative fires vary from 35% to 55% efficiency; you don’t have to be a professor in mathematics to work out the difference.

I think it is fair to say that if you look at the difference between a house with only central heating from a gas fired boiler or a home with an additional fire, it is fair to say that the fire is only interesting from a decorative point of view.

The so called flue-less fires are very efficient because they don’t have a flue as the name indicates, and therefore all the heat the produce stays in the room. They do have two downsides. One is that all the models I have seen, still need that big hole in the wall. The second one is where they are the opposite of roomsealed boilers, which is probably what more than 90% are. Whereas the roomsealed boiler blows all the fumes to the outside, the flueless fire “blows” all the fumes into the room. In theory, that is fine because of the catalytic converter that should make sure that what comes out is nothing else than water and carbon dioxide ( CO2 ). But what happens when that part fails? It doesn’t bear thinking about, which is probably the reason that the vast majority of my colleagues don’t want to install them.

The moral of the story: if you want a nice fire because it gives character to the room, by all means get one installed. But if it is from an economy point of view, be aware that it won’t save you a lot of money, and quite possibly will be more expensive than using the boiler to just get the cold out of the room.

Boiler repair prevention

Getting your boiler repaired fast, professionally and without needing a second mortgage is great. Even better, is if you don’t need to call a heating engineer because it all works fine. I’m sure this is not the first time that you hear someone venture that prevention is better than a cure. The principle is old, tried and tested, and hard to argue with. The question of course is: what can you do to prevent central heating trouble and the resulting inconvenience and cost?

In an ideal world, you would have had a top-quality boiler installed, by a top engineer, completely by the book, and than religiously service every year. Sadly, this is planet earth where a lot of things are not entirely perfect. Chances are that the boiler was there when you bought the house, you have no idea who installed it and even less so if it was done to spec, or that some corners were cut. In the vast majority of cases there is no service record at all, and even if there is, you don’t know if it was a full strip down service, or just a probe in the flue, and a wipe with the dustrag.

What has been done, has been done, but that doesn’t mean you can’t improve your chances. The first thing to do, is to get a reputable heating engineer to service the boiler and check the whole system over. That includes inspecting any visible joints for signs of problems, and radiators and valves for signs of leaks and corrosion. Check if pipes are damaged in any way like dents of parts that have buckled. Both are likely to have weakened the pipe; sometimes only so little that it is fine to leave it place, sometimes it is safer to cut the bad part out and replace it. The best time for these kind of jobs is summer, or whatever passes for that in this country. Somewhere between April and September.

Establishing a professional working relationship with a local boiler engineer this way, will save you a lot of hassle as well as money in the long run. When you do the non-urgent jobs before they become urgent, it can be done at a mutually convenient time. It also gives you a chance to check the man out when you are not fully dependent on him. Presuming that all goes well during the initial job, the client now has the certainty of knowing someone who is good at what he does. At the same time, the engineer will know you as someone who is reasonable with what is required, and pays the bill when it is due. Plumbers are human too, and we are much more likely to do a bit extra for existing clients, like coming out after 6 o’clock, or trying to help you re-ignite the boiler over the phone.

Central heating and threeport valves

Central heating valves come in a variety of flavours. They are often referred to as zone valves, diverter valves, threeway or threeport valves or boiler valves as if they are all one and the same thing. You guessed it: they are not. They come in different sizes, different brands, different systems and different applications.

The most common models, made by a variety of manufacturers, are moved against a spring when activated. This swings a rubber ball that normally rests against an opening, away in order to allow flow to run.

The combination of timer/programmer and thermostat will energise a small motor which holds the valve open as long as there is a call for heat or hot water production.

The simplest version is what is know as the zone valve. As the name indicates, they are used to activate different zones. On most older systems, there is one zone for the central heating and another one for the hot water. One of the main advantages of using zone valve in stead of threeway valves, is that the amount of zones is unlimited. As underfloor heating is slowly but steadily gaining in popularity, it is not unusual to find one zone for the “normal” heating, one for the cylinder, and one for the ufh. The downside of zone valves, is that they must have a by-pass, which can cause problems when it is not set properly.

The advantage of threeport valves, is that they do not necessarily need a separate bypass, and that there is only one needed for basic two zone systems. The first versions of threeway valves, were called diverters. They had an option for Domesic Hot Water (DHW) on only, or DHW as well as central heating. Only later came the more modern threeport valve that has the option of one, or the other, or both. This has a major advantage, especially when used in combination with an independent programmer. When the hot water production is set to come on before the heating comes on, it will heat the hot water cylinder up a lot faster. Likewise, when the cylinder is already satisfied, the radiators will warm up much faster when all the available capacity from the boiler is reserved for the radiators only.

The other version of valves that do not work with a spring as mentioned above, is known as motor-on-motor-off. In stead of the rubber ball being lifted to allow flow, there is a paddle that is rotated. The motor is only energised for as long as it takes to move the paddle to the required position. When that is achieved, the valve does not remain energised, but remains open or shut until the demand changes.

Combiboilers and second pumps

Combiboilers and pumps generally don’t go together, but it is amazing how often I have found systems with extra pumps. People enquired how much it would cost to install a shower pump or extra heating pump because the radiators don’t get hot.


There is the odd exception where a pump has a function in the situation where a combiboiler does not work properly. In a few, rare cases, the mains water pressure is insufficient to provide sufficient hot water. The solution would be to install a breaktank with a pressure booster. It does however have disadvantages, one of which is the storage of water in a container that is open to the atmosphere. This has the potential of developing unacceptable bacteria levels, especially in summer.

Another possibility, is a large radiator system with a higher flow restriction than the internal pump of the combiboiler can handle. Rare, but nevertheless possible. In the majority of case where people want to install a second pump, the problem is not caused by pump capacity, but by blockages, bad piping of the radiators, blockages, or wear of the internal pump of the combiboiler. Although a second pump would possibly help, it is the wrong solution.

Powershowers or showerpumps simply never have any use with a combiboiler. There are three reasons why a combiboiler that is not defective, can have a lack of hot water production.

The first one is an undersized gaspipe. This can lead to insufficient gas reaching the boiler, which prevents it from working at full capacity.

The second reason is lack of flow due to a restriction of the incoming mains. A showerpump increases the pressure, not the flow, and will therefore be pointless.

The third reason, is lack of pressure on the incoming mains. A showerpump can only boost the pressure if there is ample water available, as there is with a cold water storage tank. With a combiboiler, such a tank is not present and therefore there is simply insufficient water to boost. As soon as the pump starts to work, an under pressure will develop at the inlet side. At the very best, there will be a minute increase, which will probably be so small that it is not even noticeable. More likely is that the showerpump will work “in a vacuum”, and perish prematurely.

Different combiboilers have different requirements, but to make a large one (35 kilowatt upward) work properly for domestic hot water production, you generally need a mains pressure of no less than 1.5 bar, and a dynamic flow rate of 20 litres per minute or more.

The difference between a boiler service and a boiler repair

The difference between a boiler service and repair may be quite clear, but a large proportion of householders can only determine when it is time for the latter. This would be at the point where the central heating fails to come on, or the the hot water doesn’t warm up any more. It is not unheard of that a householder notices a problem with the central heating and comes to the conclusion that the boiler needs a service.

Although it does happen that that is all it needs, it is rather rare. Recently during a repair in Brockley SE3, it turned out that what stopped the boiler from working was a combination of dirt causing a poor flame picture, corrosion which stopped the rectification current to run correctly and drifted gas valve settings. This would have been prevented from happening if the system had been serviced annually. There were other problems as well, which made the job into a real repair rather than an overpriced service. What surprised me most, was the amount of smaller problems that apparently had never been spotted by anyone that serviced or repaired it before. For those of you that don’t know the Brockley SE3 area in south east London, on average it is a reasonably affluent area where you expect it to be possible to find a decent heating engineer.

Some faults were less obvious than others, but something like a flue that was neither supported properly, nor sealed at the wall on the outside or inside, is something that is hard to miss. It is not a big job, and not difficult either; just a bit of sand and cement mortar around the flue on the outside wall will sort it out. This stops water ingress that can cause quite a bit of damage over the years in the form of rot or mildew stains, and prevents fumes coming back into the home in extreme cases.

The next rather obvious problem was a couple of small leaks from the pipes connected to the boiler. If they are really small and the little bit of water escaping dries up before it can go anywhere, it can take a while before you notice them. But like most of south east London, Brockley SE3 has very hard water, so before long there are the telltale white/grey calcium stains.

There was a similar leak which is not unknown to happen on this particular boiler on the inside. The connector for the automatic airvent on this model is known to be a bit feeble, and that, too, had been leaking for a long time.

Luckily for the owner, it could all be rectified before real damage was done, and without it costing hundreds of pounds, so I hope my reputation for sorting out boiler problems in Brockley SE3 has been increased yet a little bit further.

The correct roomtemperature for central heating

Whenever I install a programmable roomstat for somebody in south London, I enter some basic settings for the owner that should be fairly close to a good compromise between efficiency and comfort. Quite often the answer to my question: “What temperature would you like?” is the question: “what it should be?”

There is no such thing as the correct roomtemperature, or the best for that matter. I know people that keep the lounge on 25 degrees Celsius, or 77 Fahrenheit if you prefer. I also know people where the room gets rarely above 17 Celsius or 62 Fahrenheit.

There is no right or wrong temperature, whatever you feel comfortable with, is good for you. 20 to 21 maybe the most common value, and often recommended, but if you don’t experience that as pleasant, there is no reason why you should stick to that.

You could argue that the getting used to lower roomtemperatures would improve your resistance against colds or flu, but I am not aware that there is actually any credible evidence of that. The only valid reason for keeping lower temperatures in your home, is the cost of heating. The less the boiler is on, the less money you pay for gas. Reducing the average roomtemperature will save you money, just as reducing the amount of hours that the boiler is set to come on will have that effect. Reducing the settings of thermostatic radiator valves in rooms has the same result. Turning those settings down half a notch will reduce the temperature in those rooms on average by about one degree. If that is not uncomfortable, you can turn them down another half notch after a couple of days. By gradually lowering the roomemperature until you have found what the limit is below which you are not comfortable, you can make a saving of several hundred pound each year if the house was kept unnecessarily warm.

copper pipe or plastic pipe

People often wonder if copper pipe is better than plastic pipe. In my humble opinion, there is a place for both. No doubt copper pipe above floor where it is visible, when it leads from the central heating radiator valve down to the floor for instance, it looks better than plastic pipe. For any gas application other than underground, copper pipe is also the only choice. For any application as central heating pipe, and hot or cold water pipe, a decent quality plastic pipe certainly has advantages. Since it comes in 25 or 50 metre coils as standard, it allows to be used in one run under a floor without any need for joints. There are several brands that offer very long warranties, which makes it ideal for those situations where the pipe is not accessible. Some examples are where floors are tiled over after installation, or hardwood parquet. A run through a concrete floor is another situation where it is advantageous not to have any joints.

Making soldered joint can also lead to problems in those areas where working with an open flame is difficult. But plastic pipe also has disadvantages. Where there is a possibility of repeated axial force, in other words where the pipe for whatever reason is pulled away from the joint, there is a risk of accumulating damage. This may after time lead to a failing of the joint. Rodent damage is another potential problem. Mice and rats have been known to develop a taste for plastic pipe, and where this happens, copper pipe will be the solution.

There is another situation where copper pipe is superior to plastic pipe; wherever there is a chance of water actually boiling. Hot water cylinders can boiler under fault conditions, and so can central heating boilers. Neither should be connected directly to plastic pipe.

Energy conservation through draught proofing

With gas prices consistently coming down less in spring than they go up in autumn, energy conservation is bound to become an issue if it isn’t one already. Where installing new high efficiency boilers is often a costly affair, prevention of waste is usually quite inexpensive. You can have the best or most efficient boiler in the whole of south London, if the heat is leaking out as fast as it is produced, you will still be facing a very hefty gas bill.

The number one enemy of keeping your house warm, is draught. Ventilation is a good and necessary thing, but having a wind blow through your warm rooms is not. Many homes have doors and windows that simply don’t shut properly and installing draught proofing strips tends to be easy and costs little. Sash windows can be improved with small narrow brushes, and doors and opening windows benefit from foam or rubber strips.

There is a variety of companies that manufacture all that you need in diy packages that can be applied with a limited amount of skill and in very little time. In most cases, all you need in terms of tools are a small hammer, a junior hacksaw, a sharp utility knife and a screwdriver.

If you want to see if this is something you are able to do, Youtube offers a large number of videos that amply demonstrate how it is done.

This is something that not only saves you a considerable amount of money over time, it also greatly increases the comfort in your home.

The correct pressure for a sealed central heating system

What is the correct pressure for a sealed central heating system, is another question that comes up many a time. In general, the answer can be found in the service and installation manual, also known as “the manufacturer’s instructions”.

The information found in these documents, should always be followed. The following is only general advice for those situations where the official guidelines can not be obtained. At all times, you should get a registered gas installer to verify that everything is safe to use if you are not competent to work on boilers.


For most central heating systems, a working pressure of between 1 and 1,5 bar is good. In general, it is a risk to have the boiler operate when the pressure in the system is below 0.5 bar or above 2 bar. When a central heating system warms up, the water expands and as a result, the pressure goes up. There should be something called “expansion vessel” connected to a sealed system. It can be in the boiler itself, or added separately somewhere else. This device is designed to limit the pressure differences that occur as a result of the temperature going up and down.

The most common way to add water to the central heating system when the pressure is too low, is though the use of a filling loop. The most common version looks like a silver braided loop of about 250 mm which connects two pipes via two valves. Although it is technically not allowed to leave that loop in place after the pressure has been adjusted, in many cases people leave it just where it is. Apart from just not being allowed, it is also safer and can avoid problems to take the braided hose off after use, and put a suitable cap on each of the valves.

Topping up the pressure on a sealed central heating system is fairly simple, and is generally considered to be a user operation.

Central heating programmers

Central heating programmers can make a massive difference to your boiler performance. The majority of these timers do not have the option to set the heating and hot water demand and different times. It used to be the rule, to size the boiler at the total output of the radiators and then add about 3 kilo Watt for the hot water production. Over the years, the absorption capacity of cylinders has increased to make faster recovery possible. As a result, the total capacity of the system is now usually much greater than that of the total of the rads plus the 3 kW.

That means that when the central heating and hot water are both on, the boiler can not match the demand. As a result, the time needed to heat up the house is longer and the cylinder does not reach the required temperature for a long time.


So called “independent” central heating programmers like the Honeywell s9400c, have the option to have the hot water on before the central hearing comes on. Let’s say you get up from Monday to Friday at seven in the morning, and the heating needs half an hour to bring the temperature in the rooms to an acceptable level. That means the heating should come on around half past six. With an independent central heating programmer, you would have the option of setting the hot water from six until half past six, at which time the hot water can be set to switch off, and the heating to come on. The full capacity is now available to heat the cylinder to the required temperature in that half hour. Modern versions of hot water cylinders only need fifteen to thirty minutes to reach 65 degrees Celsius. A temperature of more than 60 degrees is needed to prevent the Legionella bacterium from developing to unacceptable levels. Once the hot water demand is stopped, all the capacity of the boiler can now go towards heating the rooms, which will now be achieved at a much faster rate than when the boiler needs to feed the radiators and cylinder at the same time.

The price of independent central heating programmers is only marginally higher than that of “standard” models, and the vast improvement in performance is well worth the few extra pounds when replacing the timer.

Boiler and central heating breakdown cover insurance

Boiler and central heating breakdown cover insurance in south London seems to be becoming a rather controversial subject. I suspect that it is not limited to only south London and Bromley, but as that is the area where I work, my experience with the subject is only in that area.

This goes both for misunderstandings about what kind of service people actually are entitled to, as for the items that are actually covered. I have been called out on a number of occasions by people that had boiler breakdown insurance, and were told that the faults were not covered. Another problem I have seen on more than one occasion, is that people were told by the attending heating engineer, that their boiler could not be repaired. Sometimes the reason given was that the boiler was too old and/or parts obsolete, and other times that the boiler was simply too old and the repair so expensive that it had to be considered as beyond economic repair. In literally none of the cases, the claims from the boiler and central heating breakdown cover insurance provider’s representatives was true. Every time, I could either repair the condemned boiler at a reasonable cost, or diagnose the problem after which it was sorted out by the insurer.


It doesn’t seem to be a single insurance provider that falls short of delivering either, as the people that contacted me had purchased insurance from a number of different companies.

I have insufficient data to come to a conclusion about how widespread the problem is, but more than enough to be able to recommend to everyone who has been told that their claim is not valid, to get a second opinion.

The most common excuse seems to be that the fault is not covered because the systems is blocked and must be powerflushed. I remember one particular case not too long ago, where this was given as the reason why the engineer could not solve the problem. All it took to get the boiler going again, was undo a connector and put it in the correct place. Once the system was working again, I used an infrared laser thermometer to check the heat image of the radiators, and it showed no problem with blockages at all. Another case fairly shortly after that in the same area, was with a householder who had been told the main heatexchanger had failed, and the cost of materials plus labour was more than the boiler was worth. It turned out that there was nothing wrong with the heatexchanger, but simply a matter of the pump being too old and worn to achieve sufficient circulation. On this particular boiler, the pump could be changed in less than half an hour, and the cost of materials was less than £100.

Although boiler and central heating breakdown cover insurance can avoid unexpected high repair bills, it is good to know that there are quite a few limitations. Another unpleasant surprise that many people appear to have had, is the time it can take to solve the problem. They were under the impression that any problem they had would be repaired within 24 hours. In reality, the only time limit the insurer had given, was to ATTEND within 24 hours, and even that with the condition “where practicable” or “reasonably possible” or something along those lines. In other words, they would try to have a look within a day, provided they were not too busy. For the actual repair to be completed, it can easily take a week or longer.

If you do decide to take out boiler and central heating breakdown cover insurance, it may be prudent to read the terms and conditions very carefully before parting with your money. Direct debits may ease the financial pain, but before you know it, you are paying in access of £200 a year (the second year’s premium is often a lot more than the introduction offer) and you may well end up still spending a lot of money because the insurance does not pay out.

Magnaclean and other central heating filters

Magnaclean and other central heating filters are often recommended and installed for the wrong reasons.

First of all, they should never be used as a solution for problems caused by corrosion. If your boiler has problems due to the build up of magnetite as a result of rust, the whole central heating system should be cleaned properly. It doesn’t hurt to install a filter after that process is completed to stop rust and or limescale particles that re-occur or reform from there on, but filters should not be used as an alternative for cleaning or flushing a system.


Central heating filters come essentially in two forms. Mechanical filters or strainers that effectively work as a sieve, and magnetic models. Some brands offer a combination of the two, others are exclusively one or the other.

Magnetic filters can be extremely effective in removing even the smallest magnetite particles, and have the advantage of not getting clogged. They therefore are unlikely to get clogged and limit the flow through the system. The downside of these, is that they do little or nothing to remove anything that is not magnetic, like bits of limescale , dust or other dirt. Mechanical filters will remove all particles, but tend to be less effective for very small bits and prone to blockages that lead to reduced flow. It is for that reason that they require regular checking and cleaning as soon as there is a noticeable amount of debris collected.That doesn’t mean central heating filters are a waste of money, there are several reasons why it is quite beneficial to use one.

The first reason, is that some systems are very difficult to flush completely clean. You can remove the majority of the gunk in them, but not quite everything. Installing a filter to catch the remaining few bits that keep floating around, can solve that problem.

The second good reason, is when you have a boiler that is particularly sensitive to problems caused by particles. Adding a filter to the central heating system can be a major factor to help avoid further problems. For the best results, a central heating filter should be installed just before the boiler, and after the last tee.

Good boilers and bad boilers

What are good boilers and bad boilers is another one of those questions that comes up time and again. Although there are some proper dogs that appeared on the British market over the years, the answer is a bit more complicated than naming brand a or make b and rate them as the best and the worst.

One reason it is not easy to determine good boiler or bad in general, is that most boiler manufacturers have had very good boilers whilst others had more than average problems.

Another subject of disagreement comes from pure pot luck. I personally know a chap who did a diy job installing a bad boiler that I wouldn’t dream of selling to my customers, never had it serviced in 6 years, and didn’t miss a beat. Another one of exactly the same type had 4 different faults before the year was over.


One thing that is bound to create problems, is going on the cheap and buying a boiler that is too small for the demand. If you have a large open plan house, or all old fashioned draughty windows, you will need a big boiler if you don’t tackle the heat loss. The same goes for people who expect to run four bathrooms off a small combi.

The most important factor in my humble opinion that determines whether a boiler will turn out to be reliable or not, is the quality of the install and the subsequent maintenance. Even those boilers that are considered to be the very best money can buy in this country, are likely to fail before too long if they are not installed correctly. The most detrimental thing for a boiler, is no doubt corrosion. The radiators, pipes and valves should be meticulously cleaned; if half possible before the new boiler goes in. If for whatever reason it is difficult to clean the system before hand, it can be done after the new boiler is installed. When the system has been thoroughly cleaned, it should be treated with a good quality inhibitor. It should also be established at the time of the install, if not before, that the system is absolutely water tight. Any leaks will only get worse and allow oxygen to get into the system, and cause the inhibitor levels to fall below minimum concentrations.

From here on the boiler should get serviced annually in order to nip any problems in the bud, rather than wait until they cause a real problem. After a bad experience with one install when I let myself be persuaded to use a bad boiler in order to keep the cost down as much as possible, I promised myself to stick to quality materials. By doing that, and working by the book, I have found that it is easily possible to keep boiler breakdowns below 0.1% per year. It is always possible that something goes wrong, even with the best quality in the world, but a good boiler backed up with a good boiler service will keep cost and inconvenience down to an absolute minimum.

Concealed flues aka flue in voids

Concealed flues aka flue in voids, will have new safety guidelines come into effect that can have serious effects for a great many people that have a boiler where the flue is not entirely visible over it’s entire length.

Anyone who has work done on the boiler from then on eg. A sercive, a repair or land lord gas safety certificate inspection, whether owner or tenant, will be told the installation is not safe. The technical qualification will be At Risk, which means the engineer will be obliged to label the boiler and turn it off until rectified unless you prevent that. Not allowing the boiler to be shut down for safety reasons will not really change the situation as the installation will still be classified as unsafe, labelled as such, and logged. For landlords, the immediate effect is that they do not comply with duty of care toward the tenants. Private owner/occupiers have a less immediate, but no less important situation because they won’t comply with the requirement from most if not all insurance companies to maintain the property safely and to a reasonable standard.



It is very easy to avoid any inconvenience and resulting costs being unnecessarily high, by taking timely action. All you need to do, is install little inspection hatches that can be opened to inspect all the joints of the flue in the void.

What exactly are concealed flues? In most cases, we are talking about boxed in parts. They may be covered because they run along the ceiling in a kitchen or bedroom/lounge. Another fairly common reason, is mechanical protection for flues that run through storage area, loft or utility room.

Installing the hatches or inspection openings is not something that especially has to be done by a heating engineer. You can do it yourself, or engage the help of a handyman/builder/carpenter. As long as all the flue joints in the void are properly inspectable, it should be fine.

Safe gas work on boilers

One of the questions that comes up time and again in south London, is who can work safely and legally on gas boilers.

The answer is simple: EVERY plumber, boiler engineer, gas engineer, heating engineer that you call out must be Gas Safe Registered for the company that you rang. For sole traders, that means he himself must be registered. For companies, there is a second option. Companies can have a company registration number, and then specify the individual gas engineers on there.

In case of doubt, you can verify whether the engineer is legal to do the work, with the Gas Safe Register by phone during office hours on 0800 408 5500.

You can verify his credentials 24/7 365 days a year online by googling “gas safe register” and the site will lead you through a quick, simple process that takes a couple of minutes at most.


 ALL legitimate registered gas installers are financially hurt by illegal cowboys, and as such I can not see any reason why a legitimate engineer would not be more than happy to give you his name, number, postcode or whatever you want to use to verify he is legitimate to work on your boiler. I am part of a large network of mostly independents and small companies who help and support each other with unusual problems, and none of those several hundred people has ever objected to helping to establish their credentials as far as I am aware.

There are NO exceptions to the rule that a professional who works on gas MUST be registered. I have heard quite a few over the years, and although some sound quite logical, they are still only excuses. The most common ones are:

It’s okay, I am just doing the preparation, somebody else will sign it off. That ONLY works for water pipes, radiators and that kind of thing. To work on gas carrying parts and flues, you MUST be a registered gas installer.

I used to be registered not so long ago. Would your insurance pay if it expired not so long ago?

I know what I am doing, I have worked for the gasboard all my life. It doesn’t matter who you worked for or how long; if you are not on the Gas Safe Register TODAY, it means nothing.

“Saturday morning jobs” is another one that pops up frequently. Guys that work for a legitimate company that do a bit of extra over the weekend on their boss’ license. The answer is simple again: if the boss doesn’t know, it is not allowed.

CORGI registration is not valid either any more. Corgi stopped being involved in gas safety several years ago. There is a commercial company that can appear to be the same club due to using the same name, but those people STILL need to be on the Gas Safe Register if they want to earn money from working on gas. A Corgi card alone is meaningless.

The bottom line is very simple. EVERY heating engineer who is paid, even one single penny, for working on gas in south London, MUST have a valid registration. The same goes for everyone who EXPECTS to be paid. Working today and getting paid tomorrow does not make a loophole to the rule.

Central heating radiator problems

Central heating radiator problems come in variety of flavours which can have a number of different causes, and are quite often misdiagnosed.

The easiest one to solve normally, is when the bottom gets hot, but the top doesn’t. Invariably, it is a matter of “bleeding”. There is simply some air that got in there, and when you open the bleeding screw to let the air out, the radiator will quickly get warm again. This only works of course if the feed and expansion tank has sufficient water in it, or in case of a sealed system: enough pressure.

If the radiators need a bit of bleeding once a year, there isn’t too much to worry about. If it happens more frequently, it may be a good idea to sort the underlying problem out. It usually is the result of some sort of corrosion problem.


Less easy to solve, but very simple to diagnose, is when the top of the radiator gets hot, but the bottom doesn’t. This is almost always a matter of longterm corrosion that left a rust/limescale mixture at the bottom of the rads. The coldspot tends to be semicircular in shape, with the top horizontally in the middle of the radiator. Various ways of treating this, depending on how much gunk is in the system, and what kind of system it is.

The most complicated to diagnose and also to solve, is when various radiators in the house have different temperatures. This can be a matter of insufficient pump capacity, faulty design/installation, the boiler not producing enough heat ( any more ), lack of flow due to blockages, or a fault in the balancing. A further complicating factor, is that this kind of radiator problem is usually a combination of factors.

To solve this in such a way that the symptoms don’t come back, you have to check every part of the central heating system. Start with an performance test of the boiler, followed by a pump test and a water quality test is in most cases what is required to find out.

Condensing boiler history

The history of condensing boilers is somewhat different from what most people think.

First of all, they have been around for quite a while. Since at least the early eighties as British built, and there is anecdotal evidence of “steamers” as far back as the thirties on the continent. They may be modern compared to the first central heating systems, which were built by the Romans, but something that is over seventy years old hardly qualifies as new in my book.

The credit for the first British condenser is usually given to Archie Kidd. He demonstrated a working model as far back as 1982. It achieved an efficiency or almost 90%, which was about 50% above average in those days. To put things into perspective: imagine finding a motor that will give you a hundred miles for a tenner in stead of only sixty five. The huge savings were accomplished with hardly any electronics. The main two ingredients were insulation and a much more effective heat exchanger. When the central heating controls are upgraded from a simple mechanical roomthermostat and mechanical timer to digital controls, even more gas and money can be saved.


It may look a bit different, but a heat exchanger is in principle pretty much the same as a car radiator, only it works the other way around. A car radiator gets rid of excess engine heat by running the water in the engine through a copper frame with cooling ribs which loses heat to the air. A boiler heat exchanger has the water running through the same sort of thing, but extracts heat from the burnt gas flowing past it. Condensing boilers are no different in this respect.

Single and multipoint water heaters as were popular in the seventies, show clearly how a simple and inefficient heat exchanger works. If you don’t quite know what a multipoint water heater is, they were commonly referred to as “geysers”. This was a common water heater model built by Vaillant.

They were little more than a slightly tapered copper mantel around the gas burner, with a copper pipe wound around it with between one and two inches of space between each winding.

It doesn’t take a rocket scientist to work out that the taller you make that mantel, and the longer the pipe wound around it, the more heat you extract from the burnt gas.

Before 1960, when the oil price was only a couple of dollars per barrel (around $20 in today’s money) manufacturers had no reason to use more expensive copper for their boilers than necessary because nobody cared about using a bit more gas. During the first oil crisis in ’73 when the price of a barrel trebled in a year, it suddenly became very interesting how much gas was used. In the following decade, a number of people/companies claimed to have “invented” the condensing boiler. Still, it took another 20 years, and legislation, for condensers to become common place in the UK.

Global warming ( and the subsequent “green” taxes ) became a hot item under Tony Blair’s New Labour government, and in 2005 condensing boilers became compulsory. That meant that from that moment on, every new domestic boiler had to be a high efficiency model, unless there were compelling technical reasons that made their installation unrealistic. The only other exception was for some listed buildings.

Boiler repair or replacement

Without a doubt, thousands of times in London and Bromley alone boilers are replaced each year whilst there was no real reason to buy a new one. The most common reasons that are given by installers is that the old one is beyond ( economical ) repair or that the parts are no longer available. More often than not, this is not entirely accurate.


Other reasons for boiler replacement that don’t quite add up are that the boiler is so uneconomical that a new one will soon have paid for itself, or that the existing model is not allowed any more. The latter is the easiest to sort out: it is simply never true. Energy efficiency requirements ONLY apply to newly installed boilers. Existing ones can stay as long as you want them to stay, as long as they are safe to use.

New high efficiency or condensing boilers will safe some money compared to traditional models, but the amount is often vastly exaggerated. Old boilers are often quite easy to maintain and won’t let you down very often, but they do use more gas to keep the place warm. Overall of a properly installed “steamer” as the condensers are called in the trade, is around 90%. Really old floor standing boilers with an open flue and the therefore required ventilation, can go below 50%. They are fairly rare though, and the vast majority of boilers from before 2005 ( when the energy efficiency rules started ) are around 70-80% efficient. Even if we take an optimistic figure of an average gain of around 20% on the annual gasbill as reason for a boiler replacement, it will take many years before the saving will have paid for the installation. Prices for boiler swaps vary wildly, depending on the quality of the boiler and the quality of the install.

The current recession in the building industry has a significant effect on the plumbing and heating sector, which makes it a buyer’s market as competition is driving labour costs down. Still, good boilers are expensive, and more often than not require an upgrade of the gaspipe. This makes it unlikely that you will get a quality boiler swap for less than £1500, and it can easily be quite a bit more. Although there is an increasing amount of installers as well as householders that see a boiler as a disposable product, my personal opinion has always been that it is pointless to replace one unreliable product with another one that is newer but equally unreliable. The choice, however, is yours and not mine.

The one reason that is easily most frequently untrue, is that the boiler should be replaced because it can not be repaired any more. I find about one per year where I recommend replacing because repairing is throwing good money after bad. It does happen, but I strongly recommend that anyone who is told that it is curtains, gets a second opinion. I make no exception for my own clients, and always advice them to ask around and ensure them that I will be in no way offended if they get somebody else to have a look before making a significant investment.

Apart from those vary rare instances where parts are simply nowhere to be found, replacement or repair of a boiler remains a matter of opinion, and a choice. That choice should be made by the owner, based on facts, not by the installer based on greed.

Carbon monoxide from gas appliances

Thanks to various carbon monoxide awareness campaigns, the majority of people have heard about it at some point and quite a few are aware that there is a potential danger here. What most people don’t quite know, is where the danger comes from.

The actual production of carbon monoxide is from burning fuel without enough oxygen. The greatest risk, is with any appliance that is not roomsealed. Most “modern” boilers are roomsealed, and therefore pose a relatively low risk compared to fires , cookers, grills, ovens and old fashioned open flue boilers. Carbon monoxide detectors are useful if they are of the correct type and used in the correct way. To find out what is a good one and what not is really too long a story to handle here. If you want to get a CO detector, ask a professional who can assess your situation and recommend on the equipment you need.

Any gas appliance can produce CO, and the best way to avoid any problems, is to have everything checked on an annual basis, and serviced or adjusted whatever is not working as it should. I can only think of 2 ways to make sure that there is no carbon monoxide threat. The first one is by using a flue gas analyser on every appliance.


The second way, is with a carbon monoxide tester designed for the purpose of testing rather than one made for household warning purposes.

The most common reason for a higher CO production than the appliance is allowed to produce, is a lack of oxygen. There are a lot of boilers and fires that need a ventilation opening to the outside, to replace what is used by burning the gas. Especially when it is windy as well as cold, people block of those openings to keep the house warm and safe gas. Understandable as this is, it is also very dangerous. You should never reduce the ventilation yourself, if you think it is too draughty for comfort, ask a registered gas installer for advice.

Ikon 23T combi repair in Clapham south west London

During a Ikon 23T combi repair in Clapham south west London I was faced with a difficult choice. The boiler was very badly installed, and in my humble opinion, of rather questionable quality. As if that was not bad enough, the parts for these are hard to get and very expensive. All and all a bit odd, as this part of sw4 is not an area where most people try to get the cheapest of the cheap.


The Ikon 23T in question had at least 3 different parts that were not functioning correctly, and would come to the best part of £500 in materials alone. Due to the awkward design of the boiler and the access not being easy, another two hundred pounds in labour was likely to be added to the bill. That brings the total to around £700 for a boiler that I would not want to classify as reliable after that.

The problem I had now, was that the Ikon 23T is only about 6 years old, which means it should not even have reached half of it’s expected life span. On top of that, my company is known to guarantee repairs are virtually always possible and replacement not necessary. But in this case, the system did not appear to have been cleaned properly at the time of installation, and the ensuing corrosion had done quite a bit of damage.

If you have an Ikon 23T or similar boiler that may not have been installed too well and/or suffered from poor maintenance, I would recommend you either get a very good breakdown cover, or start planning on replacing it.

Viessmann 100W boilers are my personal favorite

Viessmann 100W boilers are by default what I recommend in those cases where a repair is not economical or reliable. Although virtually anything can be repaired, if patching it up is expensive and unlikely to give several more years or reliable service, you can wonder whether you shouldn’t cut the knot. If you are possibly moving out in the next couple of years, I’d be less inclined to do so, but if you just moved in, this might be the time for it.


Earlier this year, I was called out to have a look and found a boiler that was 20+ years old, had several problems, and required several hundred pounds in parts. That was a typical case of end of the ride, so there is now a nice new Viessmann 100W combi boiler on the wall.

This is probably the most under rated brand in Great Britain. It is fully German made, and strikes the perfect balance between technology and simplicity. It has all that it needs to be efficient, safe and reliable, but not all those extra frills that have little real use and only add more parts that can go wrong. One of the nice features, is that the electronics are very well protected against water from leaks or cleaning.

The Viessmann 100W boiler comes in a 26 kW, 30 kW and 35 kW combi, and in a 26 kW conventional open vent model. They are basic, simple and robust machines and in the two years that I have been using them, I have not had a single problem with them. Easy to install because there are very modest requirements in terms of space or ventilation, and the can be mounted on plasterboard walls by using a plywood “frame”. Most brands do not allow this, but the Viessmann 100W is so well insulated that it is safe to do.

Just about every standard timer, programmer and thermostat will work on these, but dedicated controls are also available including weather compensation. The heat engine is made of stainless steel and comes with a ten year warranty, whilst the rest has a five year full parts and labour back up. It may not be a work of art to look at, but the Viessmann 100W is built to last.

Combi boiler vs conventional with a cylinder

Should I get a combi, or a conventional boiler with a cylinder, is one of the most asked questions. It is also one of the hottest subjects of debate, richly spiced with a mixture of misconceptions, urban myths outdated believes.

Both systems have advantages and disadvantages, and are predominantly a matter of preference rather than technical necessity. Many an “expert” will tell you that combination boilers are only for flats. The simple response to that one is: it is not true, and never has been.


Slightly closer to the truth, is the opinion that a combi can only be used in flats or small houses with one bathroom. This is accurate, for the smallest models of around 20 kilowatt output. Back in the eighties, that was about all you could get, and in the nineties it was still the majority of the market although more powerful models were available.

During the past 5 years or so, various manufacturers introduced combis in the UK market with outputs of 35-40 kW. As nobody ever argued that a 20 kW output could not run a bathroom, 40 kW can run two bathrooms. There is a pre-condition, and that is that the incoming water mains has sufficient flow and pressure to serve the boiler. A minimum of 1 bar dynamic pressure and 15 litres per minute flow will normally do the job, but 1.5 bar or more and about 20 litres per minute flow will be better.

For areas where the pressure frequently sinks to below 1 bar, it is important to choose a combi with low requirements in that respect. It is also important to remember that every floor up, reduces the pressure by about 0.3 bar. In other words: if the pressure is 1 bar at ground floor level, 2 floors up it will only be about 0.4.

For areas that are notorious for water pressure problems, it would generally be more convenient to choose an open vent or system boiler and a vented cylinder with a tank in the loft. A tank can be filled with a pressure as low as around 0.1 bar, and will form a buffer to supply the water from. The downside of an open vent system, is that the tank is open to the atmosphere. That means amongst other things, that the water is susceptible to bacteria concentrations growing to above acceptable levels for human consumption. The cylinder temperature will also have to be set at 65 degrees Celsius. This is the recommended minimum temperature to kill off the Legionella bacterium; the cause for Legionnaires’ disease.

For households with a large domestic hot water demand e.g. 3 showers likely to be used simultaneously, you either need two combis, or a large unvented cylinder. This type of setup also needs a large incoming mains water supply and plenty pressure to work properly. That usually means that the entire water pipe needs to be upgraded all the way back to the streetvalve. Together with the significant costs of installing the unvented cylinder, that means it is an expensive exercise.

Diy boiler repairs

Diy boiler repairs is a very tricky subject, which is why I must start off with emphasizing that this blog is NOT in any way encouraging you to do anything that is not safe. You should never attempt to do any repairs unless you are competent to do so and can do it entirely safely. Even aspects of central heating that technically are not part of the heating, can still cause dangerous situation if you do them wrong.

You can compare the question: “Can I do boiler repairs myself?” with the question: “Can I drive after I had something to drink?” I would assume most people would be able to drive safely after just one drink, but I surely wouldn’t want to take responsibility for it. This blog is intended to point out a number of risks, and is in no way to be seen as a manual or guidance.

The most common repair that people attempt, is probably the replacement of the pump. It seems so simple: old pump out, new one in and job done. Some of the things that can cause problems are:

wrong type of pump

wrong size/power

still water in the pump, and maybe even under pressure.

electrical connections wrong/too loose/too tight

pump not sealed properly leading to water damage or an electrical hazard if it gets into powered part.

Similar to the pump in this respect, are diverter problems. They also have water running through them and tend to work on electricity. An added problem about diverter repairs is that the electrical connections are far more diverse.

Pcb aka board repairs can be a lot more than just disconnect and reconnect a bunch of cables. Two pcb’s that look identical, can actually be for different boilers and do different things. Some determine how much gas is burned, or what the maximum temperature is, and can leave the boiler working totally different from what it was. It is also without a doubt the most often misdiagnosed replacement.

Fan repairs are similar in the way that a lot of them look absolutely identical, but are in fact quite different. Minute differences may lead to carbon monoxide production, let fumes out of the boiler, or with certain boilers even lead to gas escapes. In some boilers, a fan that is replaced in the wrong way, can also ruin the pcb.

Just because a repair has nothing directly to do with the burner, gasvalve or thermocouple/pilot light, doesn’t mean it is automatically safe. Another classic example is the flush or powerflush. If not done right, it may not solve the problem; I have seen that more than once. Using the wrong chemicals may do more harm than good, and the same goes for not removing them properly.

Skeptics may say that a heating engineer has a vested interest in discouraging people from doing their own repairs and that we are biased. To those I would say: in all likelihood, 99% of people that read this blog would not even live in my catchment area of south London. The remaining 1% still has the choice of hundreds if not thousands of heating engineers, and the chances that scare tactics would actually lead to a noticeable increase in profit for myself, are pretty slim.

In case of doubt, ask yourself if diy boiler repairs are worth the risk.

Gas leak repairs

Gas leak detection

Gas leaks come in all kinds and sizes, just like most things. During my work as a heating engineer is south London, I have come to realise how many people are unsure what to do when they suspect a gas leak. It is neigh on impossible to come up with an example and procedure advice for every variation, but in today’s blog you will find the most common situations and what to do about it.

The most important thing to remember, is that you should always approach a gas leak situation from a worst case scenario. If you think there MIGHT be a gas leak, treat it as if there IS a gasleak. If you are sure there is one, but you don’t quite know how significant, treat it as if were a big one, and so on.


In south London, they are called Southern Gas Networks, and their number is 0800 111 999. They have professionals that answer the phone 24 hours a day, 365 days per year, and will quickly assess the situation and tell you what to do.

No matter what the outcome, no matter what happened and no matter whose fault it is, they will come out to make the situation safe as soon as possible. You will also be advised on what to do and what not to do whilst you are waiting. If you want to put your mind at ease about that, just ask whilst you are on the phone.

Gasleaks can appear in 3 different ways:

They can be in a gasappliance e.g. fire, cooker or boiler.

They can be in the gaspipe anywhere from the meter to the appliance.

The leak can be in the service pipe leading in to your home.

In the first two options, you could potentially make the situation safe by turning off the gas emergency control valve. This is the handle that is usually found next to the gasmeter.

If the leak is in the service pipe, there is really nothing you can do yourself, which is one of the reasons you should always contact professional.

South London is pretty densely populated and has therefore a significant number of emergency engineers on call all the time. The response time is normally really good, and on a number of occasions my clients told me that they were there in less than half an hour and the problems was sorted before they knew it.

If the engineer recommends to have any work done in addition to what they did, you can find the areas covered by my repair service in the link below.


Glowworm betacom repair in Dulwich SE21

A recent repair of a glowworm betacom in Dulwich showed clearly what the results can be of poor installation work. In a way, I could understand why a heating engineer would have been fed up with this job. For starters, that part of SE21 is next to impossible to find a parking space at all. This particular road was a red route for quite a distance from the flat, so at any time it was a bit of a walk to get tools and materials on site. As if that was not enough, it was a top floor flat with a very narrow staircase.
However, the new owner of the flat was now stuck with a Glowworm that did all sorts of things apart from glowing, let alone burning. The betacom is no more complicated than your average boiler, but it can be awkward to work on due to the way it is designed. Some of the specific challenges of Glowworm Betacoms are described in more detail on the page dedicated to them.

If there is plenty of space around it, it’s not so bad. This one had not. It did give me a good idea for the blog though; creating a list of things for house or flat buyers to watch out for. For those that recognise items here but already have bought the place, it is not too late. If it is still working more or less as expected, you now have time to find yourself a good local boiler repair specialist, and get him to give the boiler a full service and a complete system check over, once the winter is over.


What are the giveaways that the installer may have cut some corners that will later on lead to unpleasant surprises?

One of the easiest things to spot for anyone, including people that are absolutely not technical, is an undersized gaspipe. In all but the most rare cases, a combi boiler will need at least a 22 millimetre gas supply. By default, combination boilers will have 5 pipes. Two are for the hot and cold water, and those can be 15 mm. That leave the heating “in and out” and the gas in 22. So if you see 2 big pipes and 3 thin ones, it is suspect.

One step more difficult is the flue. On condensing boilers, the flue should go slightly up toward the outside. Standard efficiency boilers should have a flue where the outside end is just a tad lower than inside. At all times, the gap where the flue goes through the wall, should be sealed with mortar on the outside. If you lift the covering collar around the flue, and you can see daylight, it’s not done properly.

Another fairly easy way to tell whether or not it was all done to spec, is to be found in the radiators. When they are all fully on, they should all be equally hot.

The next easy one is air in radiators. If you need to bleed them a bit once a year, that is not the end of the world. If you find significant amounts of air coming out on a regular basis, there is something wrong.

The last one that is easily recognisable, is only for condensing boilers. You guessed it: the condensate outlet.
The condensate pipe should be made of the standard white overflow pipe indoors, and either the same but well insulated if it goes outside, or a larger size 32, or even better 40 millimetre. It should always go down, either vertically, or with a slight slope. The slope is called “fall” and should be a minimum of 4%, which is half an inch vertically for each inch horizontally.

Why was it so obvious that this particular Glowworm Betacom was not installed correctly? It had all of the above failures, which first lead to an intermittent fault, and finally completely stopped the boiler from working. I repaired it for the time being, and will go back when it is a bit warmer and make sure that the owner won’t have the same problems in coming winters. One more client in SE21 who will not freeze up next year.

Potterton Suprima boiler repair in Ashburton CR0.

The Potterton Suprima is another excellent example of boilers that are far too often written off as beyond repair. They can have their problems, and sometimes it can be a bit of a challenge to find where the trouble began.

This is one of those boilers where one part that goes wrong can take out another. When the heating engineer working on it doesn’t know the trick, he will replace the broken part when he finds it. But because it is not the only problem, the boiler still doesn’t work. The combination of seeing his investment in parts go up in smoke, combined with the treat of defeat can now easily lead to the verdict: “Beyond (economic) repair”. The report to you will be that unfortunately it is time for a new boiler.


The Potterton Suprima is usually set up as a so called open-vent boiler and has external controls. In at least nine out of ten cases this is either a y-plan or s-plan. Both versions have, or at least should have, a timer/programmer, a roomthermostat, a cylinder thermostat, and either a divertervalve/midposition valve, or two or more zone valves. The one with the two zonevalves is called s-plan, and the one that has one diverter is called y-plan.

Whenever the programmer is set to come on for either domestic hot water or central heating, and the thermostat is at a higher temperature than present, the control system will send a signal to the boiler to come on. If that sounds like the problem could be in the controls in stead of the boiler, you are right.

There is a third reason these boilers get condemned as beyond salvage. For some reason, they can be quite prone to blockage with corrosion residue. Although in reality this is not actually a boiler fault, it does cause it to go in almost constant “lock out” mode. As no real repair will cure this, it has more than once lead to a completely unnecessary replacement.

Apart from a few peculiarities, the Potterton Suprima is a quite sturdy boiler and in virtually all cases worth restoring. There must be quite a few in the Ashburton area, and as there is ample and free parking in that part of CR0, I’ll be quite happy come and have a look with my normal 100% result guarantee if you have any central heating problems.

Condensing boiler myths

Myths about condensing boiler repairs are as common as ticks on a hound in south east London. In today’s blog, I will correct some of the ones I hear most frequently.

Condensing boilers only last five years. This was without a doubt the most heard argument against high efficiency models when they became compulsory in 2005. It is also the easiest one to prove wrong, as all the ones I have installed over the years still work.

These modern boilers still have to prove themselves. Condensing boilers have been around since before the second world war; there is nothing new about them.

A condensing boiler is unreliable. Even more interesting, than that all the ones I installed still work, is the fact that over 90% of them never even broke down. That is well better than the track record of the average standard efficiency boiler.

You can get a government grant that pays for installing a condensing boiler. Unfortunately, this is not true. Certain categories of vulnerable people can apply for a subsidised install, but that has more to do with their personal circumstances than with energy efficiency or carbon foot print reduction.

Condensing boilers are only compulsory for certain types of houses. By default, every boiler that is installed, whether as a whole new system or as a replacement, has to be a high efficiency model. Only when there are specific technical difficulties can the engineer get dispensation of this rule.

Condensing boilers only use half the gas of other boilers. Unfortunately, this is marketing spiel of those that want to sell more of these. Although there are a few extremely inefficient heating systems that waste so much energy that the end results is a loss of more than 50%, most of the time the gain is only expected to be between ten and twenty per cent.

All condensing boilers need a 22 millimetre gaspipe. This is really complete nonsense. It may be a very small majority, but some can run on a 15 mm supply, a lot of them will need 22, but quite a few need even more e.g. 28 mm. There is no way of telling until the engineer has done a survey, and most certainly there is not rule, regulation or law that says they must have a 22 mm gassupply.

Open vent boiler breakdown prevention.

Open vent boiler breakdown prevention.

Quite amazing how many open vent systems I still come across, more in Bromley than in south London, but they are everywhere.

Most houses have the tanks in the loft, and usually a large one and a smaller one, about a foot long is the standard size. The large one is for the bath and the hot water, so we leave those alone for the moment.
I had a nice one in Bromley BR1 the other day with an old floorstanding Potterton Kingfisher and a balanced flue. Not hugely economical, but a new thermocouple placed in the right position, and away it went.

An open vent system has typically a vent pipe that goes over the top of the little tank, and than comes down.

Check your feed and expansion tank from time to time. The water level should be fairly low, about one third full is fine. It should not be full when it is cold, as the water needs to be able to expand when it warms up. It must not be too low either; the feedpipe coming out near the bottom of the tank should always be submerged.

The water should be clean; if it is anything than clear or very light tea colour, the system needs cleaning. If you clean it before it causes problems, the cost will be lots less.
If the water is brown, you’ve got a problem. Not a big one, but you need to tackle it before it gets bad. The same goes for clearish water, but with noticeable sediment at the bottom of the tank.

One of the common causes of brown water in the headertank of an open vent boiler, is what is known as overpumping. If at any time you can see water coming out of the overflow pipe above the tank, it is time to call a heating engineer.

Another common problem is the need for regular bleeding of the radiators, or sometimes only one or two rads. This can either be caused by air being drawn in, or by corrosion.

If the feed and expansion tank is not at the correct level, air can enter the system and if that leads to the pump running dry, it will soon mean the end of it. A decent pump alone will set you back the best part of a hundred pounds, and unless you are good at diy, there will be labour on top of that. Worth climbing into the loft a couple of times a year.

The last section you should check from time to time on open vent boilers, is the tank filler, often referred to as the ballcock or ball valve. The arm needs to move freely, and when it goes down, the water should start to flow are a reasonable rate. When the water is at the required level, it should stop completely.

If the checks you have done are not satisfactory, you know where to find me before it becomes a real problem.


Powerflushing in south east London

Powerflushing in south east London.

Powerflushing is one of the most misunderstood subjects and possibly the most misquoted subject of all the myths I have come across working in south east London. It is also without a doubt one of the most commonly used cop outs for “heating engineers” that couldn’t find the problem, or just wanted to create some extra billable hours. There is a number of situation, for which powerflushing offers the best solution, but more often than not there are alternatives and frequently even better solutions.
One thing that invariably does little or nothing to clean a system, is draining and filling up again with clean water.

A very common problem in south east London, is the accumulation of dirt and debris in central heating systems. The so called “open vent” systems are susceptible to this than sealed or pressurised systems, but all systems can suffer from it. In most cases, it is a combination of dust, limescale and rust.
When this happens with combis, it is usually the tap or shower that in stead of staying at a constant temperature, goes hot, cold, hot, cold.
A combination boiler that suffers from this problem, is one of the standard examples of where powerflushing is likely to solve the problem fast and efficiently. The reason is that the the alternating temperatures are caused by a blockage in the secondary heat exchanger. You can take the boiler apart and clean or replace this separately, but when you stick it all back together again, the problem is likely to come back sooner rather than later. This is because the rest of the system still contains large amounts of dirt, that will collect at exactly the same place.

Powerflushing, provided it is done correctly, will clean the whole system: pipes, radiators as well as the boiler including the secondary or plate heatexchanger.


What will it not do?
It is not a miracle cure, and it will not repair a broken boiler. It will not penetrate pipes or radiators that are completely blocked. Another thing it will not do, is create leaks. Especially open vent systems that often lose a small amount of water every day by evaporation can have tiny leaks that have been there for years but never have been noticed. The dirt and limescale have plugged these leaks, and when powerflushing cleans that away, they suddenly become noticeable. I always compare it with a screw in a tyre. Most of us have experienced finding a nail in a tyre,without the tyre losing pressure. Would you say it is best to leave the screw in, because removing it causes leaks? Of course not. Keep driving around with the screw in the tyre, and sooner or later you find your self stranded.

The other example where powerflushing is an unbeatable option, is when there is little time and for whatever reason the system needs to be cleaned as soon as possible. For all other situations other than a combi or need for speed, there are other options than a powerflushing to solve the problem.

Boiler service in south east London

Boiler servicing in south east London can be quite different, depending on who does the job, and which model you have. Some of the newer condensing types which are known in the trade as pre-mix or band A, have the facility of testing if they need taking apart to clean out completely, or not. You can measure things like fan pressure or a current, and if it is below a certain value, the boiler needs a full service aka stripdown.
Some of the larger companies will use flue gas analyser to measure the amounts of carbon monoxide and carbon dioxide on every boiler, and if that is below a certain value, they only need to do a couple more checks to legally comply with the minimum standard.
Especially older models, and by that I mean anything that is not a condenser, tend to benefit from a full strip down and cleaning session. Burner out and either a good once over, or twice over, with a brush, or blow out with compressed air. A visual check of the fan impeller and if needed a careful treatment with a soft brush. The fins on the heatexchanger tend to be coated with some dirt and/or corrosion, which also should be removed. An inspection of the rest of the boiler for any signs of leak or corrosion of other parts, and removal of dirt and debris from the combustions chamber follows.
When you spot a tiny leak, it can often be rectified by tightening a connector or replacing an o-ring or a washer. Leave this going for a few years, and the small leak may rot a hole in the boiler. I’ve seen more than one case where simple tiny drop caused a complete write off costing a couple of thousand pounds.
Another very important point of boiler service, is checking for signs of corrosion inside the system. There are various ways of doing this, and a number of symptoms that are dead give aways. Sometimes you can suffice with just adding a bottle of inhibitor. If it is a bit more severe, you may need to drain and fill the system a couple of times. If it has been going on for years, the system may have to be cleaned properly.
Over the years I have noticed throughout south east London and Bromley, that clients who call me every year for a full boiler service, seem to have fewer problems than those who don’t.


Heating engineer, plumber or gasfitter

Heating engineer, plumber, or gas fitter, who should I call for my central heating boiler repair in south east London?
The real answer, of course, is whoever will repair your boiler without too much delay and if half possible without charging you the world. Although you could define each profession in such a way that there are clear differences, in reality there are large overlaps. All three can repair water leaks and repair or replace pipes.

A specialist heating engineer should in theory be able to deal with all aspects of heating including boilers, cylinders, all the various forms of controls, but also fires, warm air units, underfloor heating, economy 7 units, infra red warmers and so on. The reality is, that anything electrical comes under the realm of electricians for one thing. Fires involve traditional chimneys as well as stainless steel double wall flues, and is usually best left to specialists. Warm air units as were popular around the sixties, also require particular skills and knowledge and thus are best dealt with by somebody who specialises in that part of the market.

Whatever the specialty, anything with gas should always be done by somebody who is not only qualified, but also listed on the Gas Safe Register database. In today’s world of 24 hours a day access to the internet, it is really simple and easy to verify that somebody is indeed registered. Anyone can google gassaferegister, click on it, and go to the verification section. You can then search by name, company or postcode. All three methods should lead to a personal listing, complete with photo. The online photo can than be compared with whoever is in your home, so you can always be sure that we are who we say we are.

After filtering out the specialties, what should a real heating engineer be able to do, what a plumber or gasfitter might not necessarily be good at?
The number one without doubt, is successfully carrying out boiler repairs. Most rgi’s will be able to install a boiler, even though some are clearly better than others. Finding out what has gone wrong when the existing installation packs up, and solving the problems, is an entirely different story. Somebody who is truly a heating engineer, is also good at diagnosing faults, tracing where the problems started, and then only repairing or replacing those parts that are broken.


There are no verified figures about who can do what, but few people that work in the industry estimate that more than one in ten is any good at repairing. The good news for you, is that there are some indicators that give you a clue about where to place your bet so to speak. As we are talking about 10% or less, the good ones tend to be busy; they are rarely willing to come out for a free quote. Contrary to the weaker brothers, they are confident that they can do the job, and guarantee results. The combination of these two characteristics usually mean that using a real heating engineer brings a faster result and considerably less expensive in the end because no money is wasted on replacing parts that aren’t broken. Many of my clients in south east London have confirmed this.

The roomthermostat in south London

The most common room thermostat I found in south east London, when I moved there, was the good old Honeywell T6360. Apart from some small alterations in the looks, it has been the same for decades. A squarish box about three by three inches, sitting on the wall at around shoulder height. A two inch dial in the middle with numbers going from 10 to 30 Celsius these days, but in Fahrenheit before that.
Still the most common room thermostat, not only in south east London, but all over the country. They are robust, need no maintenance, work on virtually every boiler under the sun and are inexpensive. The only “downside” to them, is that they are relatively inaccurate, and can have two or three degrees between clicking on and off.
The usual place to install them in the old days, was in the hall or near the stairs. This worked ok when most people only had the heating on an hour in the morning and a couple of hours in the evening, and the little dial was all the the control there was.

These days, we tend to have a much increased demand for heat, both longer and higher, and controls have become much more complicated and sophisticated. The link below leads you to a step by step guidance on how to use the whole set in the most effective and convenient way.


Today, there are many different manufacturers that each provide a range of choice in systems.
The standard model as described above is still quite popular due to its high reliability, ease of use and low price. The difference is, that they really should be installed in the lounge, and not in the hall. This is due to the working of the complementary parts that make the living room a more suitable place than the hall.

At the other end of the scale of the simple thingy on wall, is the programmable wireless room thermostat. My personal favourite is the Siemens REV24F. You don’t see a whole lot of them in south east London for a number of reasons. The first is that it is the latest model and only has been produced for a couple of years. Other reasons are that the the name is not the first one that comes up in the mind of the general public for this kind of thing. It is also at the very end of the spectrum, and therefore not in everybody’s reach when it comes to programming correctly. Once that is done in the right manner by the heating engineer that installed it, it is very easy to use from there on. As it is one of the best available for British domestic market, it is not one of the cheapest either. But it is the only one of its kind that I have never seen go wrong.

Without a doubt the hardest thing to grasp for people, is the fact that this type of control does NOT have an “off” position. How can a controller always be on, and still save energy is a very common question. The answer is surprisingly simple.
Where the old fashioned combination of timer and roomthermostat had on and off periods with a set temperature for whenever the boiler was on, this type will always come on if the temperature falls below the programmed value for that particular time of the day.
Most of these programmable roomstats ( as they are called in the trade ) have three to five separate periods during the day. During the night, you set them at anywhere between eight and twelve degrees Celsius, depending on how hardy you are. Personally, I like it nice and cosy when I get up, so for the first hour I set it a bit higher. After that, it can go down one or two degrees. Not only does that save money, staying used to temperatures below twenty also makes you less susceptible to colds and flu.
During the day if nobody is in, you can use the same as night temperature, and in the evening, you can pick whatever value suits you.
The advantages of this system are that you will never have the house get so cold that it takes too long to warm up, and you ALWAYS have automatic frost protection. Even the smallest of frost damages is likely to pay for the “expensive” controls.

Between these two ends of the scale is a variety of other roomthermostats. There are simple wireless models, and the more complicated hardwired programmable digital roomstat. Not very common, but still around, are the types that look like the old fashioned “mechanical” dial on the wall version, but actually work electronically. These are the one I personally like the least, because in my mind they combine the worst of two worlds.

On my travels in south east London I frequently get asked what the best roomthermostat is. I’d say it depends on the client and the situation.

Condensate pipe repairs in south London

Condensate pipe blockage repairs are one of the most common faults in south London that I solve during the winter months.
Virtually all condensing boilers dispose of the condensate they produce via a syphon and twenty one millimetre plastic pipe; it is usually the same white pipe as old fashioned cistern overflow pipe. What it should NOT be, is grey or white pushfit pipe, copper pipe or steel.

If this overflow pipe is “terminated” internally, which means connected to a waste pipe inside the house or flat, it can be run completely in twenty one millimetre and left at that.
If it is connected to a waste pipe or soil stack outside the house, it needs at least some foam insulation or lagging. Better is to enlarge it to a minimum of thirty two millimetre, sometimes still indicated as 1 ¼ inch, or forty mm also known as 1 ½ inch.

As for all outside waste pipes, it is vital that they run in straight lines, and always go down a bit. Any deviation from this can cause small pockets of water that are likely to freeze up and need a repair, as soon as the temperature goes below zero for a few hours even though south London tends to be less exposed than the country side like west Kent or Surrey.

If you have any small condensate pipes outside your property, you’d do well to give them a bit of protection for the winter. Personally, I always have a look during boiler services where possible to see if there are any obvious things that are likely to go wrong. I usually have some lagging with me when I drive around in south London, and can install that on unprotected condensate pipes after the original job is done, for a nominal fee since I’m there any way. Saves you the nuisance of being without heating until it is repaired, and less costly as well.

Water stopcocks and boiler repairs

Water stopcocks and boiler repairs may not seem directly related, but it is very useful to know where the valve is to turn your water off. In south west London, where countless properties have been refurbished, split into flats, changed from commercial into residential and various other major building works have taken place in many cases, the water stopcock can be anywhere.
In most cases, emergency call outs are charged by the hour, and wasting time trying to find where you turn off the water can add unnecessary costs.

There is a variety of central heating problems that you can not sort out the problem without turning the water off. The most obvious one is a leaking pipe or connection. For combis, you can add diverter valve, flowswitch, and filling loop to name but a few.
For open vent boilers, it is usually only tank fillers, taps and pipes.

In London houses, there are three common places where you find the water stopcock.
1.In the basement.
2.Under the floor, near the front door.
3.Under the sink, or at least where the sink originally was located.

In a flat, especially in converted or refurbished ones, it can literally be anywhere, including outside the flat in a communal area or even at the neighbour’s.

In 99% of cases, the water to the entire building can be turned off with a valve in the street. Unfortunately, these valves can often not be found, or be completely seized.

Next time you are bored and looking for something to do, go and have a look for your inside AND outside water stopcock. If you already know where they are, it is still a good idea to have a quick check to see that they are still working and not leaking.
Be aware that streetvalves sometimes turn off one house or building, sometimes two, and in pre-war London areas, four and sometimes even more than that can be turned off by one and the same streetvalve. Good to remember if you want to stay on friendly terms with your neighbours.


Site map for boiler breakdown repair London

HTML Site Map

Last updated: 2011, December 13

33 pages
Boiler breakdown repair south London
Boiler And Central Heating repair Cons in south east London and Bromley
flue gas analysers for boiler repairs in bromley south east london
Baxi Combination Boiler Repair Bromley
Combi Boiler Repairs South London
Potterton Puma Combi Boiler Repair in Dulwich south east London
Condemned Boiler repair Bromely south east London
Boiler repair in South London
South London emergency boiler repair central heating engineer
Local Plumbing Repairs South London Bromley west Kent
Emergency Plumbers In Dulwich south east London
Boiler replacement or repair south London
Boiler Faults Repaired in Bromley south east London west Kent
Broken boiler repair in south east London and Bromley
Boiler Breakdown Repairs Bromley South East London
Locations local emergency boiler repair south east London Bromley west Kent
Boiler Repair FAQs for Bromley and south east London
South London Boiler Engineer
Boiler Repair Service south east London
Powerflush south east London central heating
Central Heating System Repairs Bromley West Kent
Water Leak Repairs in South London
Central Heating Service in West Kent
Emergency Radiator Repairs south east London
Home Boiler Repairs South London Bromley west Kent
Condemned Boiler in Croydon central heating boiler repairs south east London
Gas boiler repairs Bromley south east London
Back boiler Repair Bromley South East London
Emergency gas leak repairs Bromley South East London
Boiler Service South London Bromley west Kent boiler repair
Fitting central heating controls south east London Bromley
CORGI Gas Safe Register Building Regulations
Boiler breakdown repair south London
The Boiler Repair BLOG

Worcester Bosch 240 boiler service in Streatham south west London

A boiler service of a Worcester Bosch 240 in Streatham, south west London was an excellent example of the benefits that an annual service of gas appliances offers. Although the central heating and hot water generally worked, the boiler would lock out from time to time. Simply resetting would normally do the job, but it is never the less a bit of a nuisance, which is what prompted the owner to book me in for a service.

During the service I found:

1.A fault with the meter which could have lead to a gas escape as well as unreliable working of the boiler, fire and cooker. The gas emergency service sorted this out the same day.
2.Damaged insulation on a cable, which could have caused a short and subsequent costs that could have been significantly higher than the price of a service.
3.Combustible materials such as feathers and leaves inside the boiler. These could have caught fire at some point and damage parts in the boiler.
4.Dirt and dust in and on the actual burner, which are likely to increase carbon monoxide production. Carbonmonoxide spillage causes many times more casualties than gas escapes.
5.The pilot light needed cleaning and adjusting, which probably accounted for most of the nuisance.

Apart from cleaning and adjusting, having an annual boiler service done


also helps to spot minor problems and nip them in the bud before they become expensive breakdowns.

Worcester Bosch CDI Greenstar repair in New Addinton

Another boiler repair in New Addington, CR0; a Worcester Bosch CDI Greenstar this time. Although the central heating and hot water were working fine, there was an odd leak that caused water to drip down on the outside wall. All I turned out to be, was the condensate pipe somehow had come out of the hopper; probably as a result of the severe storm recently.

The Greenstar is quite a different boiler from the old “normal” CDI, although both are pretty good.


This was not a big deal at this moment as was to be expected from Worcester Bosch CDI Greenstar,  which is a good quality machine, but if you don’t rectify it, it may completely break off in the next storm and cause water to build up internally and can easily cost hundreds of pounds in damp damage.

With the frost due to arrive soon and New Addington being one of the higher parts of CR0 making it colder than the rest, the boiler will be used more and therefore produce more condensate. This water can run down the wall, reach the path/pavement and freeze up there, creating a safety hazard.

Leaking/dripping condensate outlets and safety outlets should not be left “because it isn’t a lot”. It is a sign that something is wrong, and when nipped in the bud, the cost is usually very little. Left over time, the bill is likely to increase significantly, and in extreme, rare cases can actually result in the boiler not be repairable.

Check on the link below to see if your boiler is really broken or that it is something else.