Power flushing
For radiators cold at the bottom, a boiler that bangs and kettles, or black water when you bleed. Clears the sludge out of the system.
Do you actually need one?
Power flushing gets sold when it isn’t needed, so here are the honest signs that it is:
- Radiators cold at the bottom but warm at the top — the classic sludge symptom
- Some radiators never get hot while others are fine
- Black, dirty water when you bleed a radiator
- Banging, knocking or kettling from the boiler
- The system takes a long time to warm up
- Repeated pump or valve failures
- You’re fitting a new boiler to an old system
Radiators cold at the top instead usually just need bleeding, which is free and takes five minutes. If that is your symptom, don’t let anyone sell you a flush.
What’s involved
A pumping machine is connected to the system and pushes water through at high velocity with a cleaning chemical, lifting the black iron-oxide sludge out of the radiators and pipework. Each radiator is treated in turn. At the end the system is drained, refilled, and dosed with corrosion inhibitor to stop it happening again. Usually a half day to a full day depending on the number of radiators.
We’ll normally recommend fitting a magnetic filter at the same time. It catches the debris that forms afterwards and it’s a requirement for several manufacturers’ longer warranties.
What it costs
| Power flush, up to 10 radiators | £400 |
|---|---|
| Each radiator above 10 | £30 |
| Magnetic filter supplied and fitted | £140 |
We’ll tell you honestly whether you need a full flush or whether a cheaper chemical cleanse will do the job.
Common questions
How long does it take?
Typically half a day to a full day, depending on how many radiators and how bad the sludge is.
Will it fix my cold radiators?
If they are cold at the bottom from sludge, yes. If a valve has failed or the system is badly balanced, that is a different and cheaper fix. We will diagnose it before recommending a flush.
Do I need one with a new boiler?
The system must be clean before a new boiler goes on it, otherwise debris from the old pipework damages the new heat exchanger and can void the warranty. Sometimes a chemical cleanse is enough; sometimes a full power flush is needed. We will tell you which.
Can it damage old pipework?
On a very old system with corroded pipes, flushing can occasionally reveal a weak joint that was being held together by the sludge. We will assess the system first and tell you honestly if we think it is a risk.