Told you need a powerflush for your new boiler?

In most homes, yes, the system needs a thorough clean first. Building Regulations guidance (Approved Document L, para 8.8) says all central heating circuits should be thoroughly cleaned and flushed before a new boiler is installed, with inhibitor added, to BS 7593. A powerflush is the most thorough of the recognised ways to do it.

The rules say “cleaned and flushed” to BS 7593. They don’t name one method. A powerflush is one of the recognised ways to clean a system, and it’s the most thorough: clean water and cleaning chemical are pushed through every radiator, one at a time, until the water runs clear.

For an older system, or one with radiators cold at the bottom, black water when bled or a noisy boiler, a powerflush is the right choice. For a newer, clean system, less may do, and we’ll tell you honestly which yours needs.

Not by name. The guidance says the system should be cleaned and flushed to the British Standard BS 7593, and a powerflush is one of the recognised methods. Your installer follows it to show the installation complies, and boiler warranties depend on it.

No. It has been in the Approved Document since June 2022, and the cleaning advice was in Building Regulations guidance before that. The new 2026 edition, which takes effect on 24 March 2027, keeps the same wording.

The engineer who fits and commissions your new boiler. They record on the Benchmark commissioning checklist that the system was flushed, cleaned and inhibited to BS 7593, and which products were used. We do the flush and give you and your installer the written details.

Worcester Bosch’s heat exchanger guarantee says the system must be flushed and cleansed in accordance with BS 7593, with a corrosion inhibitor added. A powerflush is one way to meet that. Its main guarantee also excludes damage from sludge and blockages.

Vaillant’s guarantee terms say the boiler must be flushed before first ignition and the water kept clean, logged in the Benchmark logbook. Failing to keep the water clean will make the guarantee void. Its 10-year extended guarantee asks for the system to be flushed, cleansed and inhibited to BS 7593.

Ideal, Baxi, Glow-worm and Viessmann all need the Benchmark checklist completed for the full warranty, and their terms exclude or charge for faults caused by sludge or dirty water. Intergas asks for a flush to BS 7593:2019 by name. Always check the terms for your own boiler.

It can be. Every maker we checked ties the full warranty to the Benchmark checklist, which asks whether the system was cleaned to BS 7593, and most exclude or charge for faults caused by sludge or dirty water.

It is our written record of the clean: your address and the date, the method, the cleaner and inhibitor used, the water test results and the engineer’s details. It supports your new boiler installation: your installer uses it for the water quality section of the Benchmark checklist, and you keep it with your warranty papers. BS 7593 is a code of practice, so there is no government-issued certificate; this is the paperwork that shows the clean was done.

Not usually. The annual service should include a check of the inhibitor in your system water. If that check, or the signs (cold spots, black water, a noisy boiler), shows sludge, a clean is the fix.

Yes. We can plan it around your installer, either just before the old boiler comes out or once the new one is fitted.

We powerflush systems with all the common makes, including Worcester Bosch, Vaillant, Ideal, Baxi, Viessmann, Glow-worm, Potterton, Alpha, Intergas, Navien, Main, Ariston and Remeha. The flush cleans the whole system, so it suits any make of boiler.

Not always. BS 7593 lets the installer choose the right method for the system. A newer, clean system may need less. An older system, or one with cold spots or black water, is where a powerflush earns its keep. We’ll tell you honestly which yours needs.

We cover East Kent, including Sandwich, Deal, Dover, Canterbury, Ramsgate, Margate, Broadstairs, Herne Bay, Whitstable, Folkestone, Faversham and Ashford.