Fixed prices · Gas Safe registered
Powerflush & Central Heating Cleaning in South London
Years of use leave central heating full of black iron sludge - it settles in radiators, clogs valves and makes the boiler work harder for less heat. A powerflush circulates cleaning chemicals through the whole system at high flow, breaking that sludge down and flushing it out.
We powerflush systems across South London from £580 depending on radiator count, with the chemicals and a magnetic filter included. And we're honest about when you don't need one: sometimes cold radiators just need bleeding or balancing, and we'll tell you if that's your case before you spend real money.
Powerflush prices
Powerflush - up to 6 radiators
£580
One-day flush or less, including chemicals and magnetic filter.
Powerflush - 6 to 10 radiators
£680
One-day flush or less, including chemicals and magnetic filter.
Powerflush - 10 to 15 radiators
£740
One-day flush or less, including chemicals and magnetic filter.
Powerflush - 15 to 20 radiators
£820
One-day flush or less, including chemicals and magnetic filter.
Radiator not heating / cold radiators
£60-£80
The diagnosis visit:
- TRVs checked
- Radiators bled
- System balanced
- Pump inspected
- Honest verdict on whether a flush is actually needed
Radiator count decides the price, not guesswork - count yours and you know the cost before you call.
Heating system care
Underfloor heating service
£110
One zone, wet underfloor systems.
Cleanser & inhibitor protection
£180
The lighter-touch alternative when a full flush isn't needed yet:
- Chemical cleanse of the system
- Corrosion inhibitor dosed in
- Carried out across two visits
Before & after
Before
AfterSigns your system needs a powerflush
Radiators cold at the bottom
Sludge settles low. A radiator that's hot at the top and cold at the bottom is the textbook symptom.
Some rooms never warm up
When the furthest radiators barely heat while the closest scorch, restricted flow is usually the cause.
Black water when bleeding
Crack a bleed valve - if what comes out looks like ink, that's iron oxide sludge circulating through your boiler.
A noisy boiler
Banging and kettling often mean debris in the heat exchanger. A flush is regularly the cure the boiler was asking for.
Slow warm-up, high bills
A sludged system makes the boiler run longer for the same heat. Cleaning it restores efficiency you're currently paying for.
You're getting a new boiler
Fitting a new boiler onto a dirty system shortens its life - and manufacturers expect a clean system for warranty claims.
How a powerflush works
Step 1
System check first
We confirm a flush is actually the fix. If your radiators just need bleeding or balancing, that visit is £60-£80 - not £580.
Step 2
Machine connected
The flushing unit joins your heating circuit, with dust sheets down and the system isolated. No mess, no drama.
Step 3
Chemical clean, radiator by radiator
Cleaning agents circulate at high flow while each radiator is worked on in turn until the water runs clear.
Step 4
Protect and prove
A magnetic filter is fitted and the system is dosed with inhibitor to slow new corrosion - then we check radiators heat evenly across their full face before we pack up.
Powerflush questions, answered
What is a powerflush?
A deep clean of your central heating. A pumping unit circulates cleaning chemicals through the boiler, pipework and radiators at high flow, breaking down the black iron sludge that builds up over years and flushing it out of the system, then dosing it with corrosion inhibitor.
How much does a powerflush cost?
It's priced by radiator count, with chemicals and a magnetic filter included: £580 for up to 6 radiators, £680 for 6-10, £740 for 10-15 and £820 for 15-20. Count your radiators and you know your price - it's confirmed in writing before booking.
Will a powerflush fix my cold radiators?
If the cause is sludge, yes - cold-at-the-bottom radiators respond especially well. But cold upstairs radiators usually mean trapped air and uneven heating can be a balancing problem, which is a £60-£80 visit rather than a flush. We diagnose first and tell you plainly which one you need.
How long does a powerflush take?
Systems up to 20 radiators are flushed in a day or less - that's what the fixed prices are based on. Heavily sludged systems can occasionally need longer, and we'll tell you before we start if yours looks like one.
Do I need a powerflush before a new boiler?
Very often, yes. Connecting a new boiler to a dirty system sends debris straight through a brand-new heat exchanger, and manufacturers expect a properly cleaned system when honouring warranties. If we're installing your boiler, we'll assess the system as part of the free survey.
More questions? Read our full FAQ or call us — we're happy to give advice over the phone.
Related services: Boiler Repair · Boiler Installation
Available across: Battersea · Putney · Balham · Tooting · Wandsworth · Clapham · Streatham · Wimbledon · Colliers Wood · Morden · Dulwich · Croydon · Thornton Heath · Norbury · Sutton · Mitcham · Carshalton · Wallington · All areas we cover
Same-day availability
Speak to a Gas Safe engineer today
Fixed prices agreed before any work starts — book online with the card above, or talk it through first.