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  • Writer's pictureJames Thompson

Power-Flushing! What is it? & how can it help?

Updated: Jan 25


Have you recently had an engineer say you need a power-flush but don't really know what is? Hopefully this blog can give you, the consumer, a better idea!

In a nut shell, the end-result a power-flush gives the customer, is a more efficient system (up to 15%) and a warmer home! Sounds like a win-win, but there are some drawbacks and hopefully this will help you make an informed decision.

Heating engineers Essex

First of all, what is a Power-Flush?

A power-flush is a way of giving your heating system a thorough clean to remove sludgy deposits that get stuck in radiators and central heating pipe work; sort of a colonic irrigation for your central heating system! I know, sounds disgusting doesn't it!

How do I know that I need one?

There are a few tell tale signs that your system is in need of a clear out!


Likely Reason

Radiators are cold at the bottom and hot at the top

This can be because the sludge is heavier than water, so it naturally sinks to the low points in the system. You'll find this more prominent in downstairs radiators.

Boiler is sounding like a kettle or loud bangs coming from it

This can be down to the boiler overheating as it cannot circulate the heat quick enough from the boiler. This is also a sign that the sludge is in the boiler!

Central heating is taking longer to heat up

This can be because of the build up of sludge on the inside of the pipe, putting a larger strain on the pump and slowing the water flow. If you think of it like high cholesterol in a blood vessel, this makes it harder to circulate blood, thus putting a larger strain on a heart.

Black dirty water when taking a radiator off the wall

The dirty water is the sludge that is still in liquid form.

Below is a picture of a pipe that we cut out as it had become too blocked.

A blocked pipe

There are many other indicators that a heating engineer should be able to help with. Please feel free to get in contact if you would like us to advise further!

Below is a diagram that may help give you a visualisation of what's going on!

dirty heating system symptoms

Picture taken from Kamco website, 3/6/23

What are the advantages of a Power-Flush?

There are many advantages that come from having a power-flush. These can be as follows:

  • A more energy efficient system

  • Prolonged life of your boiler - e.g. helps prevent damage to the heat exchanger*

  • The prevention and removal of blockages

  • Help eliminate the cold spots on your radiators allowing a better heat emittance*

  • Allow a better flow of water, reducing strain on the central heating pump

  • Help reduce the risk of corrosion and rust to key components

* Sometimes if the sludge has not been properly dealt with in time, it can be too deep rooted and it may mean the boiler and/or affected radiators will need replacing. If this is the case we can provide you with a free, no obligation quotation. Please get in contact if this is something you would like.

Are there any risks or disadvantages?

Extreme care should always be taken by your heating engineer and a walk through of the system should take place beforehand, just in case there are any visible weak points. Although all this can be checked, sometimes weak joints that may be hidden under floors, in walls etc cannot be checked and on a very rare occasion can then cause a leak during the power-flush due to the increase in pressure. Although this is very rare, it is always something to be considerate of.

We recommend that you always get a professional to do this and do not DIY it or get the local handyman from the pub to do it!

Also, if you have a micro-bore system (very small radiator pipes), a small blockage can actually be moved on to a manifold, which can actually cause a bigger problem than you may well of had before. We tend to advise against this unless it is absolutely necessary. There are alternative methods including a chemical cleanse, where, rather than forcing any sludge, you allow nature to take its course and drain out under the general pressure of the heating system.

Again these scenarios are rare, but with all the benefits, we at South Essex Plumbing & Heating Ltd believe these massively out weigh the rare risks.

So, how is a Power-Flush carried out?

First of all your heating engineer will have a look over your heating system to make sure there are no suspicious looking joints that could leak. Also you may find they will use a magnet to check over some common problem areas, especially if you have an old gravity fed system (tanks in loft).

Your heating system will then be connected up to the power-flush machine, which is essentially a huge powerful pump on wheels! Depending on your system, it will be connected to the circulation pump (in the boiler if it's a Combi), or if there is a suitable magnetic filter, it may be hooked on there.

The massive pump will push a cocktail of specially formulated cleaning chemicals at a huge amount of pressure, through the pipes to help force the gunge through the specialised magnetic filter and then out of the system.

Each radiator is flushed one at a time with particular attention taken to the problematic ones.

The waste water is then dumped and replaced with clean water with a mix of corrosion inhibitor, which will help slow down the process of this building up again.

The below diagram shows a standard set up an engineer may use.

Power-flush set up

Picture taken from Kamco website, 3/6/23

How often should this be done?

In a perfect world, this should be carried out every 5 to 6 years to help maintain the system water quality. If you notice any of the symptoms noted earlier on, then it is definitely worth getting yourself some advice. Most homeowners tend to get a power-flush done when they have a boiler replaced.

If you would like us to help with this, please feel free to drop us an email or a call.

How much will a power-flush Cost?

A lot of this depends on how many radiators you have. On a typical 3 bedroom house with 8-10 radiators, we will charge around £500.

If there are more than 10 radiators, that will mean there are more chemicals needed and more time so with this an extra cost would be applied.


A Power-Flush is a great maintenance task you can have carried out on your heating system. Not only would it make your heating quieter, it will also help make it more efficient and will improve that all important coziness in the cold winter months. It also helps prolong the life of your boiler, which you've probably spent at least a couple of thousand pounds on when it was last replaced. The question is, why wouldn't you want to protect it and get the best out of it?

There are some risks in having a power-flush, but in our opinion here at South Essex Plumbing & Heating Ltd, the benefits far out weigh the risks.

If you live in the Essex area and would like some more information or to discuss anything further, please click the link below and it will direct you to our contact us page.

Thank you for taking the time to read this blog and we hope you enjoyed it.


Director and Engineer

South Essex Plumbing & Heating Ltd

Heating engineers Wickford



SEP&H came out to us and provided this solution to the satisfaction of my wife and I. Highly recommend their services and provide great after care which means we feel supported in the maintenance of our heating!

- Damian, Essex

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