How much does a power flush cost in the UK?
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A power flush typically costs £300–£500 for a small home (up to 10 radiators) and £500–£800 for larger properties. The cost is usually calculated per radiator — expect £80–£120 per radiator, with most engineers quoting a flat rate for the job.
The price should include: connection of the flushing machine, chemical cleaner and neutraliser, flushing all radiators and pipework, and a corrosion inhibitor added to the system at the end. Check this is included before agreeing.
A magnetic system filter is strongly recommended after a power flush (and when fitting a new boiler). This traps metallic particles before they reach the boiler. Fitting a filter at the same time as a flush costs £80–£150 extra but is well worth it.
Signs you may need a power flush: radiators are cold at the bottom (sludge has settled), brown water comes out when you bleed radiators, the system is noisy, hot water is slow to come through, or a new boiler is being fitted to an old system (most boiler manufacturers require a flush to validate the warranty).
A power flush is not always necessary. A chemical flush — adding descaler and inhibitor through the system without specialist equipment — costs £100–£200 and is sufficient for mildly contaminated systems. Ask the engineer to assess before recommending the more expensive option.
After a power flush, add corrosion inhibitor (such as Fernox F1 or Sentinel X100) and check levels annually. This prevents sludge from building up again and extends the life of your boiler and radiators.
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