Layout Curve
Power flush cost Compare Boiler Quotes

How much does a power flush cost? UK Prices for 2024

Central heating systems and boilers are the types of things that we tend to take for granted. We turn on the tap and expect hot water to come flowing, and when the thermostat is turned up that the radiators will throw out comforting warmth.

Get fixed prices online in just 20 seconds – Click here

So, how much does a powerflush cost in the UK?

But to operate at their best, they need regular servicing, and when we don’t do that, we have the dreaded boiler breakdowns.

Power flushing is one of those things that doesn’t get considered until there are issues and then, of course, comes the concern of how much it will cost.

Because there are many factors that will determine what the power flush will cost, it’s hard to provide an accurate figure without knowing more details. The number of radiators, for example, will have a significant effect on the cost.

As a rough guideline though £400- £500 is the average power flushing cost for a boiler and heating system within a medium-sized home with an average number of radiators.

Get a fixed price in 20 seconds

What fuel does your boiler use

Compare Quotes 

How does a power flush work?

When you power flush a central heating system it shifts all the blockages with a burst of chemicals and water.

The chemicals help to break down the sludge and any other debris which has accumulated in the system. This can cause breakdowns of central heating boilers, reduced boiler energy efficiency and a lower heating system power to then be able to keep your home warm.

Get fixed prices online in just 20 seconds – Click here

How do I know if my central heating system needs a power flush?

Needing to regularly bleed the radiators

If there seems to be a constant requirement to bleed the radiators to get the heating system working, then that can be a sign of debris build-up.

Cold spots on the radiators

This is one of the key signs of a sludge build-up. Those cold spots are being caused by the sludge blocking the path of the hot water.

Waiting longer than normal for the central heating system to warm up

If you find that you’ve been home for a while and the temperature still hasn’t gone up, then that’s telling you that the heating system isn’t operating as efficiently as it should.

The pipes are hot but the radiators are cold

When the pipes are hot you know that the boiler is producing hot water. That then means that parts such as the heat exchanger within the boiler are working as they should. The problem is that something is blocking the route of the hot water and affecting the radiator temperature.

Discoloured water coming from the radiators

When you bleed the radiators, the water that comes out should be clear. If it’s discoloured or even worse you see dirty water, then that’s a sure sign of power flushing being needed.

A noisier central heating system and boiler

Everything has to work harder when your heating system is all clogged up. So, that means that there is going to be more noise as your boiler system tries to force the hot water to where it needs to be.

Having some radiators that don’t heat up

If there seems to be no rhyme nor reason as to why one radiator heats up and another doesn’t, then it might be a sign that you need a power flush put through the system

Radiator leaks 

When the water is trying to force through the sludge, there are going to be points within the central heating system that has very high pressure. And it’s that high pressure that will quickly find any weak points and result in radiator leaks.

If your heating system is experiencing any of these problems, then now might be the time to have your system power flushed.

Do be aware though that all these can be symptoms of other issues and unrelated to the quality of the heating water. These might include problems with the heat exchanger and the water pump.

That then makes it even more important to get a qualified heating engineer to inspect the central heating system before you book a power flush.

What is the power flush cost for my home?

Now, this is a little bit like the length of a piece of string and that’s because there are several variables that have a huge impact on the price of a power flush for your home.

The number of radiators, whether it’s a new or the best combi boiler or even an old system boiler will all influence the power flush cost. And where you live can also have an impact on the cost.

The average cost we’ve detailed in the different scenarios below assume a combi boiler, that the entire central heating system is to be flushed and that there are no other central heating problems.

For a house with six radiators

For this set-up, you can expect to pay an average cost of between £300 to £350 for the power flush to be completed.

For a house with seven radiators

With increased radiators, the power flush costs increase to around £400 for a professional to do the work

For a house with ten radiators

To power flush, a central heating system costs £500 to run 10 radiators..

Flush vented systems

The majority of all boilers are now what’s classed as running on a sealed system. And that’s no matter whether you have a combi, regular or system boiler. If however, you have a flush vented system that has a feed and expansion tank, usually located in the roof space, then you can expect to pay more for it to be power flushed.

In this situation, you can expect the cost of a power flush to increase by around £300.

What are the steps in power flushing?

1. Initial power flush

First of all, the heating engineer will check all of the radiators to look for cold spots; this will tell them where the blockages are.

Because there can be a risk of water splashing from the power flushing pump, carpets and furniture are then protected with dust sheets. Next on the list is to test the pH of the water so that the engineer gains a greater understanding of the scale of the problem.

Then all of the radiators valves will be opened, and the power flusher will be connected to the pipework. This initial flush uses a range of products including debris mobiliser and scale and corrosion inhibitor.

After 20-30 minutes, the initial flush is completed.

2. Loosen debris

Now each radiator is isolated in turn and a rubber mallet is used to free up any debris and sludge which has become stuck to the inside of the radiators. This is because radiators rust inside when there is contaminated water and this rust then creates problems.

3. Second power flush

This second power flush requires that once again each radiator is isolated and cleaned by forcing the water back and forth until it eventually runs clear.

4. Full system flush

Now, the flush is run through the entire system until the water runs clear. 

Then an inhibitor is added and that’s also run through the whole central heating system. This will prevent future build-ups.

4. Final check

With the radiator valves refitted, the heating system is turned on. The engineer will then check the temperature of each radiator to ensure that they are within 10 to 20% of each other. If there is a bigger difference, then that would indicate that there is still debris within the system.

Now the radiators can be bled to remove excess air and the power flush is complete.

How long does a power flush take?

As you’ve seen this is not always a quick process. Larger central heating systems with high numbers of radiators are going to take much longer to power flush than where there is a handful of radiators in a small home. Generally, you should factor in one day for an average three-bedroomed home and two days for larger properties.

The scale of the problem will also contribute to how long the power flush takes to complete. If the central heating has a considerable build-up of sludge and debris, then the engineer may need to carry out additional flushes to get it all out

What are the benefits of power flushing?

Power flushing takes time and it’s not always a cheap process. That means that there need to be some pretty impressive benefits. So, we’re pleased to tell you, that there are some enormous advantages of having a power flush put through your central heating system.

Reduce your heating bills

When your heating system is having to work harder to force the water through the pipes it’s going to cost more to run. Whereas an energy-efficient system will cost less to provide you with all the hot water and heating you need.

So even though there is a cost involved in power flushing, you will save money through lower energy bills.

Improve reliability

Both your boiler and central heating system need annual boiler servicing to keep them in good working order. But when you have sludge problems then it’s likely that you’ll need to schedule additional maintenance because of the damage that it’s causing.

Once the debris is cleared with the power flush, the heating system becomes much more reliable and much cheaper to maintain.

Achieve consistent heating

When you have sludge blockages in your central heating system, then you end up with cold spots on the radiators. These are created when the hot water isn’t able to get all around the radiator because the sludge is blocking its way.

Once the central heating power flush is complete and the sludge is gone, then hot water is now able to run through all of the radiator and pipes in a consistent way. Now you can enjoy consistently hot radiators and get maximum efficiency from your boiler.

Increase the lifespan of your central heating system

When the sludge causes blockages it increases the pressure in parts of the heating system as the boiler tries to force the hot water through the pipes. That then means that weak points such as joints and bends can become brittle over time and that then results in leaks.

With the sludge cleared out the pressure is now consistent across the whole of your central heating system.

Increase the lifespan of your boiler

Not only is the central heating system placed under increased pressure but the boiler is too. That’s because it has to work harder than it’s been designed to, to be able to force the water around the system. It also has to deal with dirty water and contaminants that can cause mechanical breakdowns and reduced efficiency.

Reduce operating noise

With sludge in the system, everything works harder to get the water through the pipes. That then means that there is going to be more noise as the heating system tries to cope with the extra strain of getting the water through a much smaller space than it was designed to do.

Improve pressure

With the sludge preventing the water from flowing freely, it creates a much lower pressure overall, across the heating system. That then means that radiators are no longer getting as warm as they should and the hot water may not reach taps furthest away from the boiler.

Improved water quality

That sludge that we keep talking about can also get into the water that comes out of the taps. So now the water that you shower in or use for cooking or drinking is also contaminated.

Power flush vs chemical flush

There are two different types of flush that can be used within your central heating system; a power flush and a chemical flush. The chemical flush is cheaper than that the power flush cost, but it’s not always going to get the results that you need.

Chemical flush

A chemical flush is a basic cleanse that can be suitable for systems with minor sludge issues. Rather than relying on high pressure, the cleaning chemicals are poured into the system and the water flow and gravity help them to circulate around the system.

As the chemical flush enters the pipes and radiators, it begins to remove all of the debris within the system. A flush is then carried out to ensure that only clean water is now within the system. It’s also usual for a rust inhibitor to be added to the water which helps to prevent the formation of rust that can cause more problems in the future.

A chemical cleanse can be a good option to be carried out as part of your annual service checklist or before installing a new boiler. The chemical flush isn’t as powerful as the power flush and so if there are years of build-up to be removed then you’re probably going to need a power flush.

What is a Magna cleanse? 

This is a relatively new flushing process that has been designed to protect your central heating system from the damage that can be caused by a buildup of iron oxide sludge. This is a two-fold process, first of all, it cleans the system and then it provides future protection through the installation of a MagnaClean magnetic filter to catch loose sludge before it can do any damage.

This protection then lasts through the lifetime of the boiler and is said to lower fuel bills of combi boilers by up to 6%.

While power flushing fixes the problem, the MagnaCleanse magnetic filter prevents the problem from happening again.

How long does a chemical flush take?

A chemical flush takes just a few hours to complete, though that of course depends on how many radiators need to be flushed.

Can you do a chemical flush yourself?

Because you’d be working on the radiators rather than the boiler itself, there is no legal requirement for a gas safe engineer to carry out the work. However, this can be a very messy job and one that can usually be completed much quicker by heating professionals equipped with the correct tools.

How much does a chemical flush cost?

A chemical flush can be as little as £100. Now this depends on the number of radiators and how blocked the pipes are. But if you’re looking at a power wash vs chemical flush on the basis of cost, then the chemical is going to be much cheaper.

Advantages and disadvantages of the chemical flush

So, is the chemical flush the right option for your central heating system?


  • A great option for minor blockages.
  • Low cost, can be as little as £100
  • Often undertaken for free during a new boiler installation
  • No pump is needed to carry out the flush


  • Where there are sludge build-ups, the chemical flush may not be effective
  • Is only able to clear small deposits of debris
  • If the chemical flush doesn’t get the heating working, then you’ll also need to pay out for a powerflush

Can I power flush the radiators myself?

Power flushing can be expensive and no one wants to have to deal with unexpected bills. So, it might be tempting to try and carry out the power flushing yourself rather than hiring an expert.

The problem is, that this really isn’t a DIY type task. First of all, you need the correct tools, so that includes a power flushing machine, not something that most of us have hanging around in the garage. But then there’s also the combination of other specialised tools, the highly pressurised water and the corrosive chemicals.

There’s a real risk that not only will you not get the job done properly, but that you’ll also create further damage to the heating system and to the boiler.

It’s way too easy to cause more damage than good with the power flushing machine. And if you damage the boiler, you’ll find that you won’t be covered under the warranty offered by the boiler manufacturers or your home insurance policy. Suddenly the power flush costs don’t seem to be so high anymore!

Hire a professional

An experienced heating engineer who holds the appropriate qualifications will know exactly what they’re doing. They’ll be familiar with the type of boiler that you have whether that’s a combi boiler or a different type of heating solution.

Local and reliable tradespeople is a great choice and their power flushing costs can be very competitive when compared to the big national organisations.

If using a local Gas Safe engineer who offers power flush services then you should check that they are certified. This is essential for them to work on a gas system. So check before booking them to carry out a central heating power flush.

Also, check that they are qualified to operate the power flushing machine. Most manufacturers run training courses to ensure that the heating engineer knows how to use their equipment correctly.

Power flush and new boiler installations

Its often recommended having the existing system flushed prior to having a new boiler installed. This ensures that the radiators and pipework are in perfect condition to allow the new boiler to operate with optimum efficiency.

Some installations include the cost of a power flush, so before booking a power flushing service to prep your system, do check with the installation company first. Some manufacturers stipulate that you must have a system flush before your boiler is installed as part of the boiler warranty agreement.

Is it time for a new boiler?

If you’ve recently power flushed your system and been shocked at how much sludge came out or if the system readings are still not where they should be, then it might be time for a new boiler. Problems such as too much pressure or even low pressure can all be signs that your boiler is coming to the end of its working life.

A new boiler for heating water and keeping your home warm is an investment purchase so it’s important to consider not only the new heating system power but also how many radiators it will need to supply and the demand for hot water at busy times of the day.

Start off the right foot with a new boiler quote and you can even spread the cost of new boiler with our boiler on finance options.

Get a fixed price in 20 seconds

What fuel does your boiler use

Compare Quotes 

What our customers think

5 Stars on Trustpilot

Would recommend

Stressed when needed a new boiler but easy process with affordable finance. New boiler installed within a few days with option for next day.

Paul Jones 5 Star on Trustpilot

We were very impressed

On the day, they came on time. Lovely people, they kept everything clean. Explained everything to me. No mess, kept me informed.

Anne Cross 5 Star on Trustpilot

Great Experience

Great experience - quick to arrange, easy to work with the very responsive online team and all installed faster than expected.

Ms Baxter 5 Star on Trustpilot

Layout Curve
Next Day Fitting Till 2pm! & £50 Off Fixed Online PricesGet Your Prices >