A power flush is a process carried out by heating engineers designed to remove sludgy build-up in the heating system boiler, pipework and radiators. A power flushing machine sends water through your heating system at high speed to dislodge any build-up of sludge, rust and other debris helping to improve the efficiency and lifespan of your system and preventing breakdowns.

Regular system maintenance (including power flushing) is the best way to keep your system in full working condition.

What happens during a power flush?

A powerful machine is connected to the central heating system which removes dirty water and sludgy build-up while introducing clean water at the same time. Chemicals may be added to the system up to 7 days prior to break down sludge beforehand and during the power flush to help assist with the flushing process. The dirty water is carefully monitored using a TDS meter and the power flush is only complete once the discharge water becomes clear and within 10% ppm +/- of the mains incoming water.

Once the power flush is complete chemicals will be added to the system to help protect against corrosion and limescale and to help maintain system efficiency.

How long does it take?

The power flushing process has several stages and can take a whole day to complete correctly.

When does my central heating system need a power flush?

Its best practice to have a system power flush carried out every 5 years or less to help maintain system efficiency. It’s also recommended to have a power flush when installing a new boiler onto an existing system.

Signs to look out for that could indicate your central heating system would benefit from a power flush.

  • Cold radiators or partially cold radiators (usually cold around the middle and bottom of the radiator but hot at the top).
  • Dark or sludgy water in the system found when replacing a radiator, pump, valve or when removing air from the system.
  • An overflowing header/ F&E tank in the loft (this could also be an incorrectly set pump).
  • The system taking a lot longer than usual to heat up.

Does a power flush need to be carried out on a brand-new system?

It is a requirement with every new boiler installation that the system is thoroughly flushed however sometimes a “dynamic flush” or “chemical flush” using clean mains pressure water is all that’s needed and not necessarily a power flush.

Is power flushing always the solution to central-heating problems?

No. If something is broken on your central heating system or inside your boiler, a power flush will not fix it. Power flushing can improve the efficiency of your system and keep it running effectively but cannot mend, for example, a faulty pump, leak or broken valve.

Because power flushing pushes water around your central heating system at high speed, it can increase pressure on any areas of weakness, such as a rusting radiator or valve. If there are any underlying weaknesses, it can lead to leaks.

If you have a failing system with an older boiler and system (if it is 15 years old or more) then power flushing might not work for you. In such cases, it would be more cost-effective to look at replacing the boiler and radiators and maybe some of the pipework rather than trying to improve a failing system.

Will power flushing remove all the sludge in my central heating system?

No. It will certainly remove a good proportion of sludge but it cannot remove all the sludge in the system. If your system is very old or badly blocked, then power flushing may not be sufficient to remedy the problem.