Watch our VIDEO to learn the basics of power flushing

What do I have to cap when I power flush an open vented system?
You have to cap the vent pipe that terminates above the feed and expansion tank in the loft AND the downfeed pipe from the F&E tank. Here is a picture on how to cap off the tank.

Power flush on single pipe system / one pipe systems?
These systems are outdated and are better to converted into a two pipe system. They can be power flushed, but the results will vary from system to system depending on how bad the sludge build-up is. In terms of cost it's probably cheaper to try and power flush it first before, replacement or conversion.

Do both radiator valves need to be shut when power flushing a system?
No, just one will work fine. Closing just one valve will stop all flow through the radiator. Closing both just doubles the work load.

Why is POWDER flushing more effective than power flushing on badly sludged up systems?
Power flushing uses water cycling around the system at high flow rates. Water is frictionless and cannot dislodge hardened sludge of the inside walls of the system. POWDER flushing adds an abrasive powder to the water, while cycling through the system. The abrasive acts like sandpaper on the inside walls, scraping off even the most hardened sludge. (Picture of a POWDER flush)

Leaks in pipes after power flushing?
These are not common unless the company that did the power flush, used acid (we don't recommend it unless you are a professional) and forgot to neutralise it when they were done or the leak was pre-existing and got plugged up with sludge. The acidic cleaner will clean the closed leak out. Acid will also damage any aluminium in the system even when used for just a couple of hours and correctly neutralised afterwards. Too many systems contain aluminium these days and that makes using acid a very specialised and not for DIYers.

Online power flush "how to guides" on DIY power flushing ?
We offer one for sealed systems and one for open vented systems

How do I drain a system that has a label saying "do not drain"?
This notice has been put on your system after a plumber has added inhibitor to your central heating water, because this water never really changes and just gets pump around over and over this chemical inhibitor will protect your system against the forming of sludge. So if you need to drain it for maintenance - simply remember to add inhibitor back into your system when you fill it as the original chemical got drained out. Putting up a new notice with the date that the inhibitor was added to the system, is considered good practice.

How to test your central heating water? Do you need a power flush?
Simply take a sample of your central heating water, fill in our online form, and post us the sample for free testing. (domestic private homeowner use only).

Can a power flush cause damage?
In the hands of a professional it is an extremely rare event and most of the time the "damage" is related to the system being so old that it needs to be replaced, not repaired. In the hands of a keen DIYer it does happen; the online manuals or guides for power flushing are all general and aimed an ideal scenarios, with a correctly installed and functioning system. Experience tells the professional how and where to connect and what to watch out for on real systems, that in reality have many possible layouts and many possible pitfalls.

Can a power flush cause radiator leaks?
Very rarely does a power flush cause the actual radiator to leak. As an estimation 1/200 chance for a leak on your radiator, if a sludge remover is used to do the power flush. When it does happen the radiator was simply too old and would have failed anyway within months of regular use. When using acid to power flush the odds would come down to around 1/20 for this reason we do not indorse the use of acid to power flush systems as standard practice and it should be left to professionals that have examined the system as see it fit to be flushed with acid..

Mains flushing of a central heating system, does it work?
Do not do it. It is not allowed to connect the mains water supply directly into any dirty/non-pure water source, as you could contaminate the public water supply if your central heating water back flows down the pipes. This will put 1000's of people, in your area, at risk of whatever bacteria you contaminate the water with if that bacteria starts to breed. It only takes one bacteria to affect 1000’s of lives, your central heating water is filled with them. This does not pose a problem, under normal use, as you are never intended to drink your central heating water and there are many British standard, rules, to keep you from doing so accidently or contaminating your or other's pure supply of drinking water.

Why is one rad left open on the central heating and will not have a TRV?
The TRV valves used on radiators open and shut as the room temperature changes. When the property gets hot they all shut, if one radiator is not left completely open at all times the pump will be pumping against a closed circuit and eventually burn out. This pressure can also cause noises in the pipe work.

Central heating valves turn to left or right ?
To open the valve (heat the radiator more) turn them left, to make it run cooler turn them to the right. If you shut any one of the radiator valves, by turning all the way to the right the radiator will have no flow and be cold at all times. (Picture of how to balance radiators)

How do I know I have a combi boiler ?
Simply look for a pressure gauge on or under the boiler it looks like this picture. If you don't have one you should have a feed and expansion tank in the loft which means you have an open vented system and therefore a system boiler.

How often to replace inhibitor ?
Firstly you simply add more, you don’t have to drain down and add new inhibitor. It depends on the manufacturer of the product as they have different recommendations; it also greatly depends on what heating system you have. Open vented systems have the added factor of evaporation which means they need the inhibitor replaced more often, while sealed systems don't have that problem (open vented systems have a F&E tank in the loft while sealed systems have a pressure guage). Some manufacturers say once a year for open vented systems and every two years for sealed systems. You can never overdose a system with inhibitor; so adding more than recommended more often than recommended will not hurt, while not often enough or not enough will. 

If boiler is replaced. Do you have to have your system flushed?
Yes, if you don't the sludge in the system will be pumped back into the new boiler causing all sorts of problems and wear on the boiler and parts. Some manufacturers will not uphold the guarantee if your boiler breaks down, unless the water quality is satisfactory. Simply draining the system down and refilling it is not sufficient.

Should a new heating system be power flushed?
Yes, there will be all sorts of metal filings, lead and debris in the system that will cause future problems unless removed. It is also a massive problem if flux (jointing compound used for joining copper pipes) is left in the system, as it may contain acid. Simply draining the system down and refilling it is not sufficient

Does power flushing clean the cylinder?
It only cleans the central heating coil in the cylinder. The hot water cylinder on an open vented system has two separated bodies of water; the hot water circuit and the central heating circuit, that heats the cold water to become hot water. Here is a picture of how that works. It is probably safer, easier and cheaper to simply replace the cylinder as flushing and de-scaling it will probably not work well enough. This procedure is not classed as power flushing.

Can power flushing damage the central heating expansion vessel?
If the company/person doing the power flush is using acid to loosen the sludge - YES. They should disconnect and cap off the expansion vessel before they start work. If they are simply using a sludge remover to loosen the sludge it would be safe to leave the vessel connected during the flush. The pressures used to power flush is never going to be a problem for the expansion vessel, as it is done at lower pressure than it normally operates at.

I have a blockage in one radiator, is it necessary to powerflush?
One radiator not working does not mean you need a power flush, it is all about water quality. Sludge in large amounts, can cause radiators to stop working, but it is more probable that one of the valves are broken. The TRV is the most likely. We do have specialized teams that do just unblocking of radiators and boilers. This guarantee results and is normally cheaper than getting a power flush on the whole system. You can get a quote online here.

Online power flushing instructions?
Are the easy to follow and do they work? If you are a plumber they are very easy to follow and the process will be easier to master. In most cases it is not as easy as that, the system outlay normally present unique challenges that can't really conveyed in a simple "do this then do that" DIY guide. We have our own online guides one for power flushing a sealed system and one for power flushing an open vented system.

How can I make my own power flushing machine?
It is possible to make your own power flushing machine. It basically consists of a pump that can produce around 100liters of flow per minute, a tank to keep the water level and a switch that can switch the direction of flow. This switch is by far the hardest part to do as it should instantly switch the flow without re-connecting the pipe configuration. Even the external magnets can be custom made - see below. For the pump you can use a impeller or submersible pump, which you can buy online or in DIY shops. (here is an online guide)

How can I make my own magnetic filter? DIY magnetic filter?
First you have to understand how they work and are built, see our picture here. The hardest part is to build the waterproof casing that should be able to withstand not just high pressures, but high temperatures. The neodymium magnet itself can be bought online. For the body of the magnetic filter it might be easiest to use high pressure drain pipe that is suitable for the high temperatures and pressures It's easy to follow our central heating power flush instructions.

At what stage should a power flush be done, when replacing a boiler?
The power flush should be done before the new boiler is turned on / commissioned, but wen it is fully connected. The boiler should be closed off while the flushing of the system is being done. When the system is fully cleaned the new boiler should be flushed to remove flux and installation debris. This is done so that the sludge in the system does not get pumped into the new boiler, the boiler can now be commissioned.

How much water is used when you do a power flush?
It depends on how large and how dirty the system is. We will estimate a 5 radiator system to give a better idea of how much water it takes. A typical 5 radiator system will use about 250liters to power flush.

Do the radiators have to be removed from the wall when doing a power flush?
No, the radiators stay on the wall when doing a power flush. The sludge in them will get loosened by hammering or vibrating them when being flushed. The power flush machine used, cycle water at much higher flow rates than the normal system pump, around the circuit which will force any loose sludge back to the machine and get stuck on the magnets. A lot of people think you can do the reverse, simply take all the radiators off and wash them out with a hose instead of using a power flush machine. This does not clean the boiler or any of the pipes on the system and that is where the sludge must be kept out off.

Do you need to fit a magnetic filter and have a power flush done? Do I really need both?
No, not really. A power flush gets all the loose sludge, that took years to form, out of the system. The whole system; boiler, radiators and pipes in between. Fitting a magnetic filter, by itself, can only remove what is small and light enough to be moved through it by the domestic pump and is not as effective as a power flush on systems with lots of sludge. Magnetic filters are great to fit after a power flush for future protection of the system as it will remove any sludge as it builds up. It will not change the result of a power flush if you only have a power flush done and NOT fit a filter as there will be nothing for the filter to remove for years to come, but eventually you will need to reflush the system.

.How often do you powerflush?
There is no fixed period answer. When you need to, is the best answer. Systems that are new and well maintained might not need a power flush for 12years, where an old system with rusted radiators might need a re-flush in 3years. It is all about water quality. You can send us a water sample for free testing or use this visual indicator.

Is a power flush covered / included in my insurance service contract?
It differs from company to company, but most of them do not include a power flush in your insurance cover. The reasons are simple; not everyone needs a power flush and it is very expensive in relation to the yearly cost of cover, if they had to include it for everyone the cost of cover will have to go up by a lot and people will be unhappy to pay for something they don't always need.

Can a power flush damage my boiler?
In the hands of a professional, it will be near impossible to damage a boiler if it's in reasonable condition. If it is 20 years old, there is a chance that it could get damaged as it is too old and should be replaced. When people DIY; it is very easy to damage a combi-boiler in particular, depending on system layout and power flush machine strength.

Does power flushing damage the pipes in my heating system?
No, the copper/iron pipes cannot be damaged buy power flushing with a sludge remover (chemical) and machine. When you flush with acid as the chemical (we don't recommend it) it could cause some damage to any pipe/s, radiators and boiler. Old iorn pipes are most likely to get damaged. We are not saying that when a power flush is done with acid, it will damage the pipes, etc. We are saying, it could, especially if it gets left in for too long or does not get neutralized correctly.

How much does it cost to add inhibitor to the system?
If you exclude the price of the plumber (if you need one) its not that expensive at all. Central heating Inhibitor costs around £10-£20 per liter, in any DIY shop like B&Q or Wickes. How much do you need? 1liter is one can and one can will treat up to 10 radiators. Simply add to F&E tank in loft or drain a radiator and add into it, before filling it again. The F&E tank is the small tank (normally) the large tank is your dringking water. You can't add too much inhibitor only too little, but there is no financial sense in adding 4 liters as you will need to drain the system down at some stage and pay £40-£80 to re-dose the system.

Can I power flush an empty heating system?
No, to power flush you need the system full of water.

Will a boiler flush fix my boiler?
Power flushing the system or boiler will only clean the water in the boiler and system from sludge that is loose and movable. Hard or stuck on sludge cannot be flushed out and the parts will have to be replaced. We do have teams that specialize in unblocking boiler and heat exchangers. You can get an online quote here.

Average cost of a power flush? How much should I pay for a power flush?
The system size, company size and geographical location are the biggest factors in determining price. There really is no hard and fast rule, as to cost. Large insurance companies can charge £630 to flush a 7 radiator system while one of our members (smaller companies) can charge as litte as £320 all inclusive. The service, skill, chemicals and equipment is the same, but the price can vary wildly.

Over pumping on open vented central heating systems. Does power flushing fix these?
It can and it can't. It is however more likely that it will not. When your system is over pumping (water coming out of vent pipe in feed and expansion tank in loft) it means that the "H" is blocked up with hard sludge and will probably have to be cut out and cleaned or you can get a POWDER flush. Please note: cutting and cleaning pipe work is NOT considered part of a standard power flush by us and we recommend our members to charge extra for this kind of work because not everyone needs it done. How does this become a problem? When you have a lot of soft sludge being pumped through your system for years, it tends to settle on the internal surfaces of pipes and harden in place. Layers build up and become partial blockages; because it has hardened standard power flushing will not always get it off the pipes or out of the system. Don't think that you can just have the "H" cut out and cleaned by it, even though it will fix the over pumping issue you will need a power flush to get rid of the large amount of soft sludge you have. You can identify hard build-up in the "H" in several ways. Firstly you can use a magnet and see if it sticks to the copper pipes, because copper is non-magnetic; a magnet will only stick to pipes if there is sludge inside the pipe as sludge is magnetic. Secondly a noisy pump is a dead giveaway that the pipes leading up to it are narrowed down by hard sludge. Another indication is overheating boilers that make kettling sounds or banging sound. They do this because the pump can't move the hot water through them fast enough, as the water expands because of the heat, in the boiler and pipes it causes pressure to build-up and therefore make noises.

To power flush or not to power flush?
Power flushing is all about water quality. If your central heating system's water quality is kept clean your chances of parts breaking and the system being unreliable dramatically reduces. We can test your central heating water for free or have a look at this visual indicator. Most of the sludge will be radiator sludge.

Some radiators work and others don't. Do I need a power flush?
Power flushing is about water quality, if your system water is dirty you need a power flush regardless. The build-up of sludge can cause the valves on radiators to stop working, which will stop the radiator from working. Radiators that don't start working after a flush, needs one or both the valves changed. If your system water is clean, just change the valves. Note: It is not always a sludge or radiator valve problem, it could be other things like the pump and it greatly depends on system layout, etc.

Questions to ask plumber about power flush?
Always use a member of the powerflush association. They will always display our badge on their website and paperwork. We are the only organization of it's type in the UK and we have a complaints procedure for members only. Using companies that are not associated with us means that they have no accountability for any work at all. If you cannot find a member, ask the local company to "at the very least" follow our 10 recommendations when carrying out the power flushing work on your system.

How often do you clean the magnetic filter on a combi boiler?
In the beginning the filter will be filling up often, clean it as often as it needs to. The black sludge will form around the silver magnet and will keep on building up until the filter is full and starts to restrict water flow. Picture of how a magnetic filter works.

What do I do if I have power flushed my central heating system and it's still not clean?
The water in your system will be clean, but if there is a lot of hardened sludge built up on the inside walls of the system, so you might still be experiencing problems. In the majority of cases the problems that stay on after the flush can be fixed by a good plumber. It will take a lot of experience to know where these problems are, our members will be happy to help. In the cases where replacing pipes is not practical you could "POWDER" flush.

Why do you get sludge in new pipes?
Sludge will be everywhere in a system (if present), it will be moved around by the pump all the time. When you fit a new radiator or section of pipe/s sludge (if present) will be moved into that section / radiator. Even in completely new systems debris and lack of power flushing can cause the premature build-up of sludge.

I had my system de-sludged but the water is still brown?
The water should be running clean before the power flush can be completed and the water will be clear for a long time. If your radiators/system is really old the water will go brown too quickly which indicates that you need to start replacing the radiators at the very least.

Can I power flush steel pipes?
Yes, there is no problem in power flushing steel pipes, as long as you don't use acid. Using acid makes it risky. The condition of the steel pipe will determine if the any leaks are caused.

Can I power flush a pressurized system / open vented system?
Yes there is no problem powerflushing these.

How do you know when to powerflush?
We can test a sample of your water and tell you if you need to - or - you can use this visual indicator.

What do I do if powerflush didn't work?
There is either a broken part on your system that needs to be replaced or if you still have a sludge problem you can powder flush your system.

Can I power flush microbore?
Yes results are not always the same and sometimes power flushing is not enough, in these cases consider either "powder flushing" or system replacement.

How long does a power flush take?
There is no exact time and it greatly depends on system layout and how much sludge has to be removed. Power flushing 5 radiators can take 2 hours or 4 hours. It also depends on the machine used and the skill of the operator.

Does power flushing fix boiler fault codes?
It really depends if sludge is to blame for the fault code. Power flushing on ly removes sludge and debris.

How to power flush a cylinder?
A cylinder has two sides; the hot water side and the heating coil side. The heating coil gets flushed when you flush the central heating, boiler and radiators. We will discuss here, how to flush the hot water side. See picture first. You will need to cut the top pipe and the cold water feed pipe (blue in picture) on the cylinder and connect the power flush machine to those two pipes. NOTE: You are dealing with water that is for human consumption and there are extensive regulation that covers procedures and precautions, to make the water safe to use after any work. These although not discussed here should always be observed. We are simply dealing with the practical process of flushing a cylinder, not the regulation that covers the water/safety etc. Once your machine is connected you will need to circulate the water until the cylinder is clean. In most cases flushing is not the best idea, replacing it would bring guaranteed results. The use of chemicals to aid in the cleaning out of the lime scale should be done only to the manufacturer's instructions and with extreme caution.

How does sludge remover work on central heating sludge?
Sludge remover is a very mild acid that breaks the sludge down into a loose powder. This makes it easy to remove if by power flushing with water at high flow rates. Power flushing is a cleaning process that uses water to remove loose sludge and debris from a system, if its not loose, power flushing cannot clear it. See POWDER flushing for more aggressive cleaning of hardened sludge.

Power flush damage. Can a power flush cause damage?
Unless acid is used to power flush (we recommend NOT to) damage to the boiler, pipes, radiators and rubbers are extremely low. It does depend greatly on the skill and experience of the power flush machine operator.

Is it save to keep the power flush machine running with the boiler on?
It comes down to experience and system layout , but in most cases there is no problem with having the boiler running, producing hot central heating water and leaving the power flush machine on.

How much should I pay for a power flush? Boiler flushing cost?
The price will depend on the size of the company, mostly. Bigger companies can charge £600+ for power flushing 6 radiators while smaller ones, like our members, will be more in the £300 range. The process, equipment, skill, chemicals and results are the same, but larger companies have higher overheads which they have to pass on.

Does sludge in loft water tank mean I need a power flush?
Only if it is the feed and expansion tank. If it is YES you would need a power flush which will clean the system and the tank.

Can I power flush my boiler and system myself?
If you have fitted radiators before and have the correct instructions, it should not be too hard to learn. There is a lot of knowledge left out of instructions, mostly to do with system layout and flow rate drop that cannot practically be thought in a manual. It will take years to understand all the variables fully. They also leave out the "DO NOTs" as most of it is complicated plumbing and plumbing terms which a DIYer will not understand even when explained in detail.

Should I power flush first and then replace my boiler's heat exchanger or the other way around?
You have to power flush your boiler and system first and then replace heat exchanger. If your system is really dirty and you replace the heat exchanger first, the sludge will simply be pumped into and block the new heat exchanger, just like the old one.

Will power flushing unblock my pipes?
If the sludge is soft, loose and movable - Yes. If the block is hard and immovable - NO. Power flushing has limits because it uses high flow rates to clean NOT high pressure. You will have to cut the block out and replace that section of pipe. If your system has solid pieces or clumps of sludge over 6mm in size, you might also have to cut the pipes because moving big solid pieces is near impossible because of the narrowest sections in radiator valves and boiler. We do have teams that specialize in unblocking pipes. You can get an online quote here.

Which way do I turn radiator valves? Left or right
All radiator valves work the same way. Turn left to open radiator tap and right to close. Opening the valve will make the radiator hotter and shutting it will make it run colder until completely cold / shut.

Will power flush stop boiler cutting out?
Boilers cut ot or "lock out" when they overheat. They normally overheat when the water is not flowing through them, there can be many reasons: Pump is broken, valves not opening or too much sludge in the system. If sludge is the problem power flushing it out should fix the problem.

Will adding sludge remover get rid of sludge?
No, it will just loosen it up and break it into a finer powder, but it will not magically disappear. Sludge is metallic, if sludge remover can make it disappear the rest of your system AND boiler will disappear as well. You will still need a power flush to remove the sludge out of the system.