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Is a power flush worth it?
When sludge is the problem, yes. A power flush brings cold radiators back to full heat and protects the boiler. When sludge isn’t the problem, it’s money you don’t need to spend. Here’s how to tell.
- 1simple cup test you can do yourself
- 5year sludge-free guarantee, with an annual service
- 1day on site for most homes
5year guarantee
Over the years, the water in your heating system slowly corrodes the inside of the radiators and pipes. That corrosion turns into a black sludge that settles at the bottom of radiators and clogs the boiler.
A power flush pushes it out. Done when it’s needed, it’s one of the most worthwhile jobs on a heating system. Done when it isn’t, it’s an expense you didn’t need.
Here’s how to tell which you’ve got.
Signs you need one
Sludge leaves clues.
- Radiators warm at the top and cold at the bottom
- Black or brown water when you bleed a radiator
- Radiators that need bleeding again and again
- Rooms that take ages to warm up
- A boiler that bangs, kettles or keeps cutting out
- A magnetic filter that fills up fast
Try the cup test
With the heating off and the radiators cool, open a bleed valve and let a little water run into a white cup. Clear water is a good sign. Black or brown water means sludge.
System check
When it’s not worth it
We’d rather tell you than sell you one.
Cold at the top, not the bottom
That’s air, not sludge. Bleed the radiator. Our radiator bleeding guide shows you how.
Just one cold radiator
Usually a stuck valve rather than the whole system. See our guide to TRVs.
A newer system
A new system should have been cleaned and dosed with inhibitor when it was commissioned. With an annual service, it rarely needs flushing.
The water’s in reasonable condition
A magnetic filter on its own may be enough. If the water is black, though, a filter alone will fill quickly, and cleaning comes first.
Valve check
What the British Standard says
BS 7593 says a filter should be fitted to protect the system, and that a filter is never an alternative to cleaning a dirty one.
What happens on the day
The heating is off while we work and back on before we leave.
Protect and connect
Dust sheets go down at every radiator and at the boiler, and the flushing kit is connected to the system.
Radiator by radiator
Each radiator is flushed in turn with a cleaning chemical until the water runs clear. The dirty water goes to a foul drain, never the garden.
The clean water test
We show you the before and after, and check every radiator heats evenly.
Protect it
The system is dosed with inhibitor and the level tested, so the sludge is slow to come back. Adding a magnetic filter keeps it that way, and it’s cleaned at every service.
Which one sounds like you?
- Cold at the bottom, black waterPower flush
Prices on the power flush page.
- Cold at the topBleed the radiator
No engineer needed.
- One cold radiatorCheck the valve
Often a stuck pin.
- Getting a new boilerFlush included
A system flush and filter come with every install.
Common questions
How often should a heating system be power flushed?
There’s no set interval. A system only needs flushing when sludge has built up. With a magnetic filter and the inhibitor checked at each annual service, many systems never need another one.
Will a power flush lower my heating bills?
It can help. A sludged system makes the boiler work harder and leaves rooms cold, so the heating stays on longer. How much it helps depends on how bad the sludge was.
Do I need a power flush before a new boiler?
A new boiler needs clean system water to stay reliable and keep its guarantee. Every boiler we install includes a system flush and a magnetic filter in the package.
Can you power flush a system with a tank in the loft?
Yes. Open vented systems with a tank in the loft can be flushed. We check the tank too, because a dirty tank can put sludge straight back into a clean system.
Will a power flush make a mess?
No. The dirty water runs through hoses to a drain, and there are dust sheets at every radiator and at the boiler.
Does Home Care cover sludge?
No. Sludge and scale damage are excluded from Home Care plans, which is why a clean system and a filter matter.
How much does a power flush cost?
It depends on how many radiators you have. Our prices are on the power flush page, and we confirm them before any work starts.
Not sure what you need? Give us a shout.
Book online in a couple of minutes or give the office a call, Mon to Fri, 9am to 5pm. We’ll tell you what we think, and if the answer is to leave things as they are, we’ll say that too.
Worcester Bosch Accredited Installer
Guarantees of up to 12 years on the boilers we fit. Gas Safe registered. Fife Trusted Trader. 400+ customer reviews.