If your radiators are cold at the bottom, your boiler kettles like an old stovetop and the system takes an age to warm up, the problem is probably not a part. It is the water. Years of rust and debris settle into a black magnetite sludge that strangles flow, steals efficiency and quietly shortens your boiler’s life. A professional power flush drives it out. Our engineers power flush central heating systems across every London borough at fixed per-radiator prices from £350, finished with inhibitor and, where the system deserves it, a magnetic filter that keeps the water clean for years. And because power flushing is the most over-sold service in heating, we start every job with an honest assessment of whether you actually need one.
Average reply under 10 minutes. No obligation.
Steel radiators corrode from the inside
London's hard water bakes onto hot surfaces
Installation swarf and old inhibitor breakdown
Assessment
Unit connected
Chemicals circulate
Refill & inhibit
Flow & temp test
Power flushing is heating's most over-sold service, and we would rather tell you the truth than sell you a day's work. One cold radiator does not need a whole-system flush; it may need bleeding, a TRV, or a single-radiator flush at a fraction of the cost. A system that is merely unbalanced needs balancing, not chemicals. A newer system with a working filter and healthy inhibitor levels almost never needs flushing, whatever a quote-hungry engineer says. And a system with very old, fragile pipework sometimes should not be power flushed at all; a gentler chemical cleanse is the safer route, and we will say so. If our assessment finds you do not need a flush, you will hear exactly that, along with what you actually need instead.
Pricing is per radiator because that is what honestly drives the work. A typical flat or small terrace with up to six radiators runs £350 to £420; a family house with seven to ten sits £420 to £520; larger homes up to fifteen radiators run £520 to £600, all including chemicals, inhibitor and the before-and-after evidence. A magnetic filter is the upgrade we recommend most, £120 to £180 fitted, because it turns a one-day clean into years of protection. And if the problem is one stubborn radiator rather than the whole system, a single-radiator flush at £95 to £140 is the proportionate answer, and we will offer it when it fits.
A flush is only as good as what follows it. Every job ends with a full inhibitor dose, recorded so your annual service can check the level rather than guess. A magnetic filter keeps collecting what chemistry cannot prevent. And here is the connection many Londoners meet the hard way: manufacturers require a clean system for a new boiler’s warranty, and a warranty claim on a sludged system can be refused. If you are planning a new boiler, the flush is not an extra; it is the condition. We coordinate both, and our installation quotes already include the appropriate clean. Read more on our boiler installation page.
Are any radiators cold at the BOTTOM?
What colour is the water when you bleed a radiator?
How old is the system since its last flush or full clean?
A Lewisham terrace, SE13: eight radiators, five cold at the bottom, water like espresso at the first bleed; flushed in a day, every radiator even by evening, before-and-after samples left on the kitchen counter.
A Winchmore Hill house, N21: flush plus magnetic filter ahead of a new boiler installation, warranty condition met, paperwork filed with the boiler’s registration.
A properly run flush uses high flow at low pressure precisely to avoid that, and where a system is genuinely fragile we recommend a gentler chemical cleanse instead and say so at assessment.
With inhibitor maintained and a magnetic filter fitted, many systems never need a second flush. Without protection, sludge returns in five to ten years, which is why the aftercare matters more than the flush.
