Central Heating system flushing

Central heating system cleaning and flushing is an often overlooked part of system maintenance, but one of the most important.

Over time your heating system corrodes, caused by water and air within the pipes, radiators and boiler, gradually building up until parts start to fail or you have a complete blockage of your pipes or waterways within the boiler.

There are several methods of cleaning as well as reducing future build-ups, while these may seem a little costly at first, these have a dramatic impact on heating bills, as well as the lifespan and efficiency of the boiler, and reducing breakdowns.

central heating system flushing

Pre power flush pipe 2 Screenshot 20191011 073754 Facebook

From the day a heating system is installed it starts to corrode! This corrosion is a natural and unavoidable reaction that happens between water, air and metals. Even the addition of inhibiting chemicals will not stop this and will only slow the process.

The resulting mixture is called Magnetite and forms a thick black substance, affectionately known as ‘sludge’, to build up within radiators, pipework, pumps, valves and inside the boiler itself, causing cold spots on radiators, poor performance, breakdowns, and in extreme situations when left untreated, a complete renewal of the entire heating system could be needed.

In 2019, the building regulations amended BS:7593 to include that all new boiler replacements should have the system properly cleaned/flushed and tested before fitting and should also include chemical inhibitors and a magnetic filter as a minimum.

Luckily, we now have several solutions available depending on the severity of this corrosion, which can be determined by taking samples of the existing system water and carrying out a few simple tests to determine the quality and what course of action is best for you, we also take samples after the flush to ensure you are left with the best possible results!

The prices quoted are stand-alone prices, these are discounted if taken as part of a boiler installation.


Adey Chems

  • Chemical Flush – The most basic and cheapest form of cleaning the system and only really suitable for cleaning out any flux/solder residue after working on the system. These cleaning chemicals are added anything from a couple of days/up to 2 weeks before removal depending on the type of cleaner used and how bad the system is, before draining out, rinsing, and re-filling the system. These help to break down and loosen the sludge making it mobile. This method can be used alone on relatively new/lightly soiled systems but is always better in conjunction with an actual flush (all flushes require chemical cleaner). We carry out chemical flushes on all installations as standard. For more info please see: https://www.adey.com/category/chemicals




MagnaCleanse system flush

  • MagnaCleanse Flush – This unit is linked in series on the return pipe to the boiler, allowing deposits to be captured before entering the boiler. This utilises the heating system pump to help circulate the cleaning chemicals while allowing us to clean the system with hot water, giving better results. This method uses the least amount of water as it cleans and recirculates the water rather than flushing it to a drain.  With this and the following methods, each radiator is opened and agitated to clean out one at a time to ensure the best possible results, but will not remove seriously build-ups or deposits.

   –   Starting at £400.00 for up to 10 radiators including chemicals. (£25.00 per additional radiator).

–   For more info please see: https://www.adey.com/category/magnacleanse

Book a MagnaCleanse Flush


kamco clearflow cf902

  • PowerFlushing – This is basically a jet wash for your heating system. We use a high-pressure machine to pump heated, chemically treated water through your system, allowing even the most stubborn deposits to be removed, but this does have its drawbacks as it can cause damage to older, more seriously corroded pipes, radiators, valves and fittings due to the pressure and velocity of the water, but even these will not clear totally blocked pipework, and therefore a renewal of the pipework to the effected radiator(s) is recommended. We use this alongside the MagnaCleanse unit to help capture the maximum amount of debris.

   –   Starting at £600.00 for up to 10 radiators including chemicals and machine hire. (£35.00 per additional radiator).

–   For more info please see: https://www.kamco.co.uk/cf40-power-flushing-pump.html

Book a Power Flush


  • Cold Flush – This is the process of using mains pressure cold water to circulate through the system to remove debris. We have a unique, patent-pending, ‘Uber-Flush’ unit that allows us to do this with the ability to reverse the flow, and in some cases use hot water which removes even more deposits than a single direction cold flush. We drain the system via the MagnaCleanse to show how much debris has been removed. The drawback with this method is it uses considerable amounts of water, and can’t be offered if the incoming cold pressure is poor.

   –   Starting at £300.00 including chemicals. (£20.00 per additional radiator)


Protection and Prevention

While after every flush, install or any other times we have to drain the heating system (for things such as repairs, replacing or adding radiators etc) we add inhibitors to your system, this alone only offers minimal protection. Even then, over time, this will become diluted as you bleed radiators/add water to the system, this is why now we have to check and top up these levels as part of an annual service.

There are now several methods to help prevent this build-up and/or protect your system and boiler.

Magnaclean cross section
Spirotech cross section

  • Magnetic filters – These have gained popularity over the last few years, so much so that BS:7593 2019 now requires them to be fitted on all new installations, alongside a chemical flush (as a minimum). These contain powerful magnets that capture the magnetic debris that could build up in the boiler or system. These are ideally placed on the heating ‘return’ pipe to the boiler so any particles will be collected and prevented from entering the small waterways within the boiler. These should be cleaned as part of an annual service to maintain effectiveness. Various filters are available for different systems and situations. For more info please see either: https://www.adey.com/category/filters  or  https://www.spirotech.co.uk/solutions/dirt/

Spirotech deaerator cross section

  • Deaerators – These are relatively new for domestic settings and are a preventative solution. As in the explanation of the forming of system sludge above, it is the mix of water and air that is the cause. These units remove the air from the system water automatically thus removing one of the causes of sludge. These aren’t protective however so should be used alongside a magnetic filter. For more info please see: https://www.spirotech.co.uk/solutions/air/