Frequently asked questions:

Watch our VIDEO to learn the basics of power flushing

Do I need a power flush?
All central heating systems should be kept clean and have inhibitor added to them in sufficient quantities to slow down the forming of sludge.
That is true for any system, regardless of layout or age. 80% of all the trouble you have or will have with your system is either related directly or indirectly to sludge / debris in your system
(That’s if sludge is present in sufficient quantities).
The only real way to know if you need one done is to have a water sample tested - we now offer FREE testing of domestic samples. Results will be emailed to you within 24 hours.
If you need a professional to have a look / give an opinion on your system and your water quality we offer a consultant visit.
If you don't want it tested or a consultancy visit the simple rule is; if you have never had a power flush done, your system probably needs it. For reference: (Picture of sludged water)

Does power flushing work?
Yes, power flushing is a very effective cleaning method and removes most of the sludge out of your system.

What is "sludge flake" and how is it different from normal sludge?
Normal sludge is mud like and does not easily block parts of your system. Sludge flake is when normal sludge has been converted into flakes of various sizes. They are rigid and easily block parts on the system, causing shut downs. It is extremely hard to remove from a system and rarely gets removed by standard power flushing without other techniques. We consider flushing out sludge flake as a specialist procedure and not all our members will be willing to work on this problem, because the results are unpredictable and it is a lot more work than a standard power flush. Read more >>>

How do I know I need a power flush?
It's all about central heating water quality. You will need to take a water sample, from the central heating water, of at least 250ml after it has been running for at least 30min. It is better to take two samples and discard the first, to get a real picture of the overall water quality. You can do that by either bleeding it out of a radiator or from the F&E tank in the loft you will need to stir the tank water to get the sediment on the bottom disturbed. We offer two separate services post your water sample for tests (which is FREE if you are a domestic home owner ) or a consultancy visit. Doing a visual on a sample yourself; Your ok if the sample looks like tap water or even if it has a slight brown tint. If it looks like brown ale you already need a power flush done. If it looks like black ale, you needed one years ago (Pictures of sludged water). It should also be mentioned that system water can appear clean when they are not, because the sludge has settled in the bottom of the radiators and pipes. The magnet sludge test: using a strong magnet to test copper pipes for metallic sludge, works really well. Copper is non-magnetic and the magnet will NOT stick to it unless there is a lot of sludge inside the pipes. If it sticks to a copper pipe, you will need a power flush. The areas most affected by sludge, on open vented systems (tanks in loft), is the pipes leading into and coming out of the external pump. Power flushing is the new minimum standard for system maintenance and loads of companies will not work on your system or boiler if you have not had it power flushed.

One radiator does not heat up. Do I need a power flush?
There are several reasons why a radiator/s can stop working. Sludge build-up is a possibility and power flushing could help fix this, but it does not always work to unblock radiators. This is especially true on microbore systems (undersized pipe work). We have created a teams, that specialize in boiler and radiator unblocking.  You can get a quote online here.

My boiler heat exchanger is blocked with sludge. Will power flushing my central heating system fix this?
It will depend greatly on where in the boiler the block is and the boiler layout. Some boiler makes are easy to flush clean, other cannot be flushed clean at all, regardless of what machine or chemicals are used. When it cannot be flushed out, you will need to power flush the system first, then change the primary heat exchanger or the sludge in the system, will just block the new heat exchanger. In combi boilers there are 2 heat exchangers; primary and a secondary (hot water) heat exchanger. The secondary heat exchanger does not always unblock when the system is being power flushed. If you are having hot water problems on a combi boiler, you will need the secondary heat exchanger replaced or power flushed separately after a standard power flush has been completed. Also read about "sludge flake" as it is commonly associated with blockages in the boiler and other places in the system.

I had a power flush done and it didn't work. What now?
There are 4 main possibilities:
- The power flush was not your only problem, in the system and there are part/s that needs to be replaced on your system as well. It is very common to need remedial work, as well.
Power flushing is a cleaning procedure and does not fix broken parts, if a part was broken by too much sludge in your system, you will still need it replaced after a power flush has removed the sludge.

- Sludge flake: This is when the sludge in the system has been converted in flake like pieces. They are large and easily block parts, pumps, pumps, heat exchangers and radiator valves. Standard power flushing does NOT always deal with this problem and is unlikely to if the flakes are big enough. This is now extremely common with over 70% of systems that shut down regularly having sludge flake in it. Read more here>>

- Your sludge problem is bigger than what a power flush can handle.

Power flushing has limits and will not clean all hardened sludge out of your system, if normal power flushing fails you should try powder flushing. Powder flushing is much more aggressive on hardened sludge and cleans much better than normal power flushing.
Standard power flushing works well on cealed systems while powder flushing is designed for older systems like open vented and microbore (under sized pipework).

- The power flush was wrongfully advised by the plumber/person who advised it and you only needed a part/s replaced
It all starts with the person who recommended a power flush. They are rarely experts in the field and often get it wrong, as they don't understand the limits, a power flush has as.
It is a common misconception to think that all boiler engineers/gas engineers know about power flushing or has been trained or experienced in power flushing systems. Power flushing and gas engineering have nothing in common and gas engineers don’t get trained to power flush as standard. The only real way to know if you need a power flush is to get the central heating water tested or get a expert in the field to survey the system. We offer a postal service where you take a water sample and post it to us for testing. You can have this done for free if you a private domestic homeowner - click here for the online form. We also offer a consultant visit, where besides taking a sample for testing the consultant will have a look at your system and give his opinion and answer any questions you have. Remember, having been "recommended a power flush" or “power flushing will be beneficial” does not mean "definitively needed a power flush".

Is it worth having a power flush done?
You will always benefit from having your central heating water as clean as possible, how much you will benefit will depend on how much sludge you have in your system. If you have never had one done it is a good idea to have a power flush to remove what has built up over time, before it starts causing problems.

Will a power flush increase my central heating's efficiency?
Yes, it will. How much will depend on how bad your system needed one, but don't expect 50% reductions in your gas bill. It's more like 5%.

What is a power flush?
A power flush is a cleaning procedure that cleans the central heating water; the pipes, radiators and boiler that the water runs through. Power flushing and powder flushing are the only modern procedures worth having done.
Power flushing: Uses a power flush machine (creates fast flowing water), chemicals (loosens sludge) and magnets (traps sludge for removal)
POWDER flushing: Uses a powder flush machine (creates even faster flowing water), abrasive powder and magnets (traps sludge for removal)
The old versions of “flushing” are:
1) Draining the system down with a hose through a drain off cock and letting the water run till clean, sometimes a chemical is added to help loosen up sludge before the drain. This procedure can be called a “system flush”, “system cleanse” or “standard flush” (useless in comparison to the modern way);
2) Taking the radiators off and washing them individually (does not clean the pipes, boiler, pump, etc.);
3) Connecting mains water to one side of a radiator valve and a drain hose to the other (subject to system pressure, location of radiator and no chemicals can be used to improve the results, also hard to move sludge when it is cold and compacted). This technique is not legal in the UK and most other countries, as you risk contaminating your local area's drinking water supply with the bacteria that is already in your central heating water which was never intended for human consumption.

How long does it take to do a power flush?
It depends greatly on how much sludge is in your system, chemicals used, setup time and where you connect into the system.
As a rough guide: 5 Radiators can be flushed in 2-4 hours, 7 Radiators can be flushed in 3-5 hours, 10 Radiators can be flushed in 4-7 hours.

Why is POWDER flushing more effective than power flushing on badly sludged up and old central heating systems?
Power flushing uses water cycling around the system at high flow rates, but water is frictionless and cannot dislodge hardened sludge of the inside walls of the system. POWDER flushing adds an abrasive powder or pellets to the water, while cycling through the system. The abrasive acts like sandpaper on the inside walls, scraping off even the most hardened sludge. It also cleans "sludge flake" much better than standard power flushing can. (Picture of a POWDER flush)

What is sludge?
Sludge is a cumulative name for rust and debris found in your central heating system water. The rust comes from you radiators ageing in the water just like a nail would rust in water. The process can be stopped or dramatically slowed down by adding inhibitor which is a chemical you can buy in any DIY or plumbing shop. That is why it's our last step in the power flushing procedure, to protect the system against rusting again after it's been cleaned. Always have inhibitor in your system.

Will power flushing remove the lime scale in my system?
It is a common mistake to think that there is a limescale build-up in your central heating system / radiators. Limescale is a mineral deposit and forms when 1000's of litres of water (rich in minerals) pass through a section of pipe, your central heating water is the same amount of water being pumped around and around. Limescale can only form in your hot or cold water pipes that supply your taps, not in your central heating system. The most common place where limescale this is a problem, is on Combination (combi) boiler systems where scale build-up blocks the hot water heat exchanger (picture). The only way to fix this is to physically remove that heat exchanger and de-scale it with a machine/chemicals, this is not classed as part of power flushing itself, but a complementary procedure or you ca have it replaced.

Does the company / person doing the power flush need to be Gas Safe registered?
NO they do not, a power flush does not have anything to do with gas. But it really helps a lot when the person doing the work has a very good knowledge of how central heating systems and boilers work and would be allowed to carry out additional works if need be. Having someone that works on boilers and central heating systems all the time, therefore "gas safe registered" will be better than one that is not. Note: Any work that requires the boiler cover to be taken off might require a gas engineer and therefore a registration with the gas safe register.

Does the company / person doing the power flush have to belong to the Power Flush Association?
They do not have to, but it is a very good idea to use one of our members. We make sure that all of our members have the necessary skill and experience to complete a power flush successfully with the least risk and best results.
We also bind our members to our Code Of Conduct, which is designed to get customers the best and safest service that will clean and not damage their central heating systems.
Our code of conduct also creates a set list of what is included in the price and what is excluded, so that customers do not get fooled into using a company at one price and end up paying much more.

Does power flushing cause leaks?
There are two categories. Flushing with acid and flushing with normal sludge removers.
When you flush without acid, leaks are not common at all. The more common "leak" is the radiator taps dripping from the top because they have not been turned in 20 years, till today. Mostly an easy fix involving tightening the nut on top. Leaks from radiators, pipes, boiler etc. after flushing happens; roughly 1 in 30 flushes whereas with acid leaks in other places is more 1 in 5 flushes. That is why we do not recommend using acid as a standard and only in extreme cases with great caution, there is now a viable alternative procedure to using acid, called powder flushing. Really old systems are sometimes beyond the help of a power flushing, but you really can tell until you have it power flushed.

When do I power flush and when do I powder flush ?
Power flushing a system is for when the sludge is light and loose in the system which normally means that the system is less than 10 years old (very rough guide and subject to system maintenance). For older systems, like open vented and microbore, the sludge would have hardened onto the internal surfaces. This process can limit the flow through the pipes down to a full block. This reduction of flow happens over many years and is not apparent until it all goes wrong. Powder flushing takes care of the hardened sludge which the chemicals used for power flushing will simply leave behind in the system, it is also extremely safe to use on metallic and non-metallic systems. An abrasive, in powder or pellet form, is used in the water when the central heating water is circulated with a powder flush machine. This "sands" the sludge down or knocks it off the internal walls, so that it can be removed. The abrasive powder slowly dissolves in the water and is finally removed by changing the water in the system, leaving it sludge and abrasive free.

Does power flushing fix leaks?
No, even though sludge often cause leaks. Removing sludge cannot fix leaks, only prevent future leaks. If your pressure on your combi boiler drops over time, you have a leak and need it fixed..

Can Power flushing fix a problem with your boiler or central heating system?
Power flushing (removing sludge) does not fix anything, it simply cleans the central heating water, pipes, radiators, boiler, etc. which will prevent it causing more or future damage. If sludge broke a part in your boiler, that part will not magically start working when it is removed. All parts of your system that is already broken, damaged or not working will need to be replaced if you want your system to work properly. Just changing the part that is broken will make the system run until sludge breaks the next thing, which does not take too long. If the problem with your system is too much sludge blocking flow in the boiler or heating system, then yes. Cleaning processes like power and powder flushing should fix the problem, because it is sludge related.

Can I DIY? Rent a machine and power flush my system myself?
Yes you can, but it would be better to use a professional if you are having problems with your system. Remember that you are not allowed to do anything to do with gas and that includes taking the boiler cover off (in some cases). Power flushing is a science, unless you are a plumber, no video on the internet page will teach you everything you need to know, experience cannot be taught at all. You can search through our members HERE.

With that said, here are our DIY guides to do it yourself: DIY power flush sealed system and DIY power flush a open vented system

What is a magnetic filter and how does it work? (Picture)
Simply put it is a large magnet in a container that is plumbed into your system. The sludge / rust is metallic and sticks to the magnet removing it from circulation and saving your boiler and other parts from getting jammed up. This filter has to be cleaned out manually every so often just like you would a vacuum cleaner; the space inside the container is not unlimited. These filters are good for future protection after a power flush or a measure to take if you can't afford a power flush but in comparison the power flush will clean your system much better and faster.

Which central heating sludge remover is best?
It is more a question of how long you leave it in your system, rather than, which manufacturer's product is better. Sludge remover loosens up the sludge and helps break it down into smaller pieces. When treating a heating system prior to flushing the manufacturers all state to leave it in for a week or more, if at all possible. For really old systems as long as 4 weeks is recommended, that said the average minimum recommendation is 2 hours with the central heating running as hot as possible. It is better to have it in for a week/s in advance, but 2 hours is mostly more practical when it's -5 degrees C outside AND the heating is not working.

How often do I need to power flush?
There is no set time frame and will be system specific. It depends greatly on: how badly rusted your radiators are and the concentration of inhibitor in the system and system age. If the inhibitor concentration in the systems is maintained well above the minimum dose you should not need to re-flush your system as often as others. In short, you need it when the sludge build-up gets too much, and it depends on your system how long that takes. Open vented systems get build-ups much faster than sealed ones. The amount of radiators on your system also contributes as each one will contribute rust/sludge at a certain rate, the more radiators the faster the build-up of sludge.

What is central heating inhibitor and how does it work?
Inhibitor is a chemical in liquid form, it prevents oxidisation (rust) of the metallic parts of your system and therefore sludge. It does need to be topped up every so many years, read what the manufacturer recommends on the bottle.

What is the recommended dosage of inhibitor for a central heating system?
It is a bit of a specialist question and is worked out at a minimum of 1 litre of inhibitor per 100 litres of central heating water. As a rough rule of thumb: 1 litre of inhibitor will be enough for 7 radiators, we have included a 30% safety margin already. Count all double radiators as two radiators. Always put more in than the recommended and always remember that when the system is drained down you will need to re-add the inhibitor. You can't put in too much inhibitor, only too little. Saying that; there is no point in going overboard, adding 2 litres when your minimum is 1 litre is practical, 7 litres is just silly because at some stage you will have to drain it all down for maintenance and replace the inhibitor.

How often do I add inhibitor to my system?
Inhibitor will stay in a sealed heating system for as long as the central heating water does. If the system gets drained down or topped up with fresh water, you will need to add or replace the inhibitor.
For open vented systems the inhibitor will evaporate over time and will need to be topped up regularly. How often, depends on the manufacturers instructions and can be anywhere from 1-3 years. You can never add to much inhibitor to your system, only too little, so adding it every year will guarantee that you have enough.

Can central heating inhibitor cause damage to my heating system?
Most inhibitors are compatible with all metals found in your system. Inhibitor will stay in your system and prevent sludge from forming as long as the dosage is high enough. It does not matter if you use your system / boiler or not, it will prevent problems not create them. Always us inhibitors that are compatible with ALL metals especially Aluminium.

Does power flushing a system always clean it completely?
Systems cannot be 100% clean. That is simply impossible, power flushing aims to clean >95% of the loose sludge in your system. The little bit that remains will not move around as the sludge before, because the machine used for the procedure is much larger and generates incredible flow rates over your domestic pump. There are parts of the system that cannot be cleaned by power flushing and will have to be cut out and cleaned or the pipe/s replaced in that section, normally this is where the down feed pipes from the water tank join in just before the pump. We call it the "H" (picture) and it is only found on open vented systems / systems with water tanks in the loft.

One of my radiators does not work. Will a power flush make it work?
Maybe. There could be so much sludge in the system that it could completely restrict flow to a radiator, but more often than not the radiator valves / taps need to be replaced as they could have been damaged. One radiator not working does not conclusively prove that you need a power flush, taking a water sample is more indicative.

Does my newly installed central heating systems need to be power flushed?
The manufacturers of the boilers require the central heating system to be chemically cleaned, for your guarantee to be valid. It will also bring down your chances of a breakdown and requiring the guarantee by up to 80%. New systems will be full if metal filings, flux, sludge and other installation debris. You will be silly not to flush it out properly.

My boiler pressure drops. Can power flushing fix this?
No. Pressure drop means a leak of some kind on your central heating system; most of the time this is caused by sludge in your system, but power flushing cannot fix leaks by removing the cause of it.

I fitted a new boiler. Do I need to power flush?
Yes, the manufacturer requires your whole system to be cleaned or your guarantee will not be valid when it breaks down. Also, it is much more likely to break down if you don't.

I replaced some radiators. Do I need to power flush?
No, unless the work involved cutting and joining pipes. It also depends on the flux that was used; some are acidic and will cause sludge to form over time.
Remember: If the system was drained down you will need to replace the inhibitor in the system.

I added a section of pipes with radiators to my existing system. Do I need a power flush?
Yes, the whole system is connected together and the whole system will need to be cleaned.

Who demands that systems should be power flushed and why?
- Most boiler insurance schemes will want your system power flushed as standard.
- Manufacturers of your boiler, before they do any work.
- Plumbers that can see it has not been done on your system.
Why? Most central heating problems relate directly or indirectly to sludge or lime scale in your system. Eliminating that would make problems easier to diagnose and prevent future problems from occurring and limiting repetitive future callouts and breakdowns.

I had power flush done recently and got told that I needed it done again. Do I need to?
If it's less than 7years ago I would get a second opinion. It is unlikely that you need a power flush if the first one was done correctly (depends on how old your system is) and if you have kept the inhibitor levels high enough, but it is possible. A water sample is the best way to tell (picture). If you have continuous problems on a really old system, read more on POWDER flushing.

Will cleaning or flushing out my feed and expansion tank be as good as a power flush?
NO, when doing a power flush the feed and expansion tank will get cleaned out. Unless your system has been flushed very recently there will always be black sludge in your feed and expansion tank. Cleaning it out by itself does not really do anything as the sludge would have settled on the bottom of the tank and not be circulation around the system at all. It  definitely does not hurt to keep the tank clean so that more sludge cannot enter the system, but 90% of the sludge is in the system itself NOT in the feed and expansion tank.

Should I power flush my system, if I am changing all the radiators?
Yes, the sludge will be spread over the whole system; pipes, radiators and boiler. Changing all the radiators does not clean the pipes; the sludge, installation debris and flux (if pipes were cut and joined) will be pumped around the system and into all the new parts.

I have had a power flush but my magnetic filter is still full of sludge?
Power flushing does not clean 100% of the sludge out of the system and it can only remove the loose or newly loosened sludge. If there is hardened sludge on the inside walls of the pipes it cannot be removed by power flushing, but there is a new technique called "powder flushing" that can. The little bit of sludge on the magnetic filter is the really small light bits that did not get removed during flushing, unless there is loads of it, you should not be concerned.

If a magnet stick to my central heating pipes; Do I need a power flush?
Copper pipes are non-magnetic while sludge on the other hand is magnetic. If a magnet sticks to the copper pipes in your system, it is being attracted by the metallic sludge inside the pipes. Yes, you will need a power flush or powder flush.

My radiators are cold at the bottom and hot at the top; Do I need a power flush?
One possible answer is that you need a power flush. The phenomenon is called stratification (water separating into hot and cold layers) and indicates lack of flow. That could be caused by too much sludge sitting in the radiator, hence power flush, but there are other possibilities; a weak or broken pump is the most obvious one. Power flushing is about water quality. If your water quality is really bad you need a power flush regardless of any other problems or symptoms. We will test a sample of your central heating water for free and tell you if you need one, you could also use our online visual comparison.

Is a "system clean", "system flush" or "chemical flush" the same as having a power flush?
NO, these chemical cleaning techniques are not in the same class as power flushing or POWDER flushing. They do work if you don't have a sludge problem and no debris present in your system. How is it done? They simply add one chemical (sludge remover) to loosen the sludge up, drain the system and ad an inhibitor (chemical) to prevent more from forming in the future. Draining the system only gets rid of the lightest and finest sludge that is in suspension in the water, the majority of the sludge stays in the system, especially heavy sludge. It will be pumped around, over and over causing future problems. When power flushing you also add sludge remover to loosen sludge up, but then crucially use a strong power flush machine to force the sludge out of the whole system. When clean you add a inhibitor. It is a much more thorough cleaning technique.

Is the chemicals used for POWDER flushing or PELLET flush available to buy in shops or for sale online?
NO, the chemicals used are not available to any other person or company to buy. We have our own manufacturers for our powder flush machines and chemicals and only one specially trained team can perform a powder flush. Powder flushing cleans hardened sludge, while power flushing is for loose or soft sludge. Click here for a comparison between power flushing and powder flushing.

Should I link the vent pipe and down feed pipe while power flushing?
NO, it is not a good idea. You will be by-passing the most critical part of the system that needs to be power flushed. You can link them temporaraly, just to clean both pipes but don't leave them linked for the main power flush.

Will power flushing remove the lime scale out of my hot water cylinder or hot water pipes?
NO. Power flushing is used for the cleaning the system on the central heating side: boiler, radiators and central heating pipes which is not connected directly to the hot water side of the system. Flushing the domestic hot water side is a very different procedure and extremely specialist, this is NOT A DIY PROCEDURE. Always use one of our specialist members if you need this done. Here is a picture to explain how the systems is seperated, the central heating is (red) and the hot water side is (blue) Not 100% sure? Please contact us.

Can't I just drain the system down and refill it instead of power flushing it?
If you have a real sludge problem "NO". Sludge is metallic rust and the bits causing problems are large clumps that are heavy. Draining a system down will only get rid of the finest lightest sludge; the real problem will be left behind. Just because the water runs clean does not mean all the sludge is out. Some plumbers will do a chemical flush; they add a chemical, days before draining the system down. It doesn't work because there is no increase in the water's flow rate and draining happens through just one flow path, when there are many flow paths in the system. It will help a little if the problem is small but 90% of the time, you are wasting time and money. Rather get it a power flush or a powder flush done from the start.

Do I have to lift up any floorboards to do a power flush?
No, power flushing is done through a radiator or a central heating pump. All connections into the system are done without lifting any floorboards.

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