Power flushing
Power flushing pushes water through the radiators and pipework at speed to clear sludge and rust. It is most often done before a new boiler goes in, because sludge shortens a boiler's life and can upset its warranty.
Who power flushing suits
Suits
- Old systems with cold spots on the radiators
- Homes fitting a new boiler to an old system
- Systems with a history of sludge
Good points
- Clears sludge and rust
- Helps radiators heat evenly
- Protects a new boiler
Watch out for
- Adds a day to the job
- Older, fragile pipework can leak after a flush
- Not needed on every system
What power flushing costs
Power flushing typically costs £500 (Power flush of a central heating system), with most jobs between £350 and £1,000. That includes VAT at 20%. Fitting takes 1–2 days on site.
What you would actually pay
Typical Power flush of a central heating system · UK- Typical installed cost Power flushing, supplied and fitted
- £417
- VAT at 20% Standard rate
- £83
- Net cost to you
- £500
If you borrowed £500.00 over 36 months at 0.0%, it would cost £13.89 a month – £500.00 in total, of which £0.00 is interest. The last payment would be £13.85.
Illustration only – not a quote, not an offer of credit, and not financial advice. Rates depend on your circumstances and creditworthiness.
Where the money goes on power flushing
| Element | Typical range |
|---|---|
| Power flush A full power flush of the radiators and pipework, with the water tested and treated afterwards. This row is the headline price and covers the range. | £350 – £1,000 |
| Magnetic filter Catches the iron sludge that wears out a boiler, and many manufacturers ask for one under their warranty terms. | £110 – £310 |
Guide prices including VAT. Your actual cost depends on your home, access and specification.
What moves the price of power flushing
- The size of the system
More radiators and more pipework take longer to flush and cost more.
- Where you live
Engineers charge more in London and the South East than in the North and in Scotland, and the regional pages show the difference.
- How bad the sludge is
A system that is lightly clogged takes less time than one that has not been cleaned for many years.
What a quote for power flushing should include
If a quote is missing any of these, ask why before you compare it with another.
- Whether the flush includes inhibitor and a magnetic filter
- Whether the system is flushed before or after the boiler goes in
- What happens if a radiator or valve leaks during the flush
- Whether the engineer is Gas Safe registered where gas work is involved
- The time the heating is off
- Whether the price includes VAT
Power flushing prices by region
Labour is most of the difference. Typical price (Power flush of a central heating system), including VAT.
| Region | Typical | vs UK average |
|---|---|---|
| London | £630 | +25% |
| South East | £590 | +17% |
| South West | £550 | +10% |
| East of England | £530 | +6% |
| West Midlands | £520 | +4% |
| Scotland | £510 | +2% |
| East Midlands | £500 | UK average |
| Yorkshire and the Humber | £500 | UK average |
| North West | £490 | −2% |
| North East | £480 | −5% |
| Wales | £470 | −6% |
| Northern Ireland | £440 | −12% |
Common questions about power flushing
Do I need a power flush with a new boiler?
Not always. An old system with sludge, cold radiators or a history of faults often does. Ask your installer what they found when they tested the water.
What is the difference between a power flush and a chemical clean?
A power flush pushes water through the system at speed. A chemical clean uses treatment fluid to loosen deposits. Which an installer chooses depends on the system.
Can a power flush damage old radiators?
It can show up weak points, so a leak after a flush on a very old system is possible. Ask who pays if one appears.
Is VAT included in the price shown?
Yes. Every price on this site includes VAT. A VAT-registered business normally charges it on boiler work, and an engineer who is not registered does not, so put quotes on the same basis before you compare them.
Where these power flushing prices come from
Guide prices are compiled from published UK price guides, converted to a price before VAT, and shown here with VAT added. They are indicative, not quotations. How we price explains the method.
- BestBuilders, boiler service cost, last updated 7 September 2026 (VAT treatment not stated; treated as including VAT and divided by 1.2)
- greatbritishenergy.com, new boiler cost guide, updated 30 October 2026, quoting Checkatrade fitted prices (VAT treatment not stated; treated as including VAT and divided by 1.2)
Get quotes for your home
A guide price only takes you so far. Local firms can price the work on your own home, and comparing a few quotes is the quickest way to see what is reasonable.
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