Power flushing is a deep clean of your central heating system. A pump circulates cleaning chemicals through the pipework and radiators at high flow but low pressure to break up and remove the black iron oxide sludge that builds up over years of normal operation.
We carry out power flushing and MagnaCleanse magnetic cleaning across Cheam, Sutton and the surrounding areas. A power flush is £550 excluding VAT for up to ten radiators, with £40 per additional radiator, and a MagnaCleanse is £400 on the same basis.
Sludge is the usual cause of radiators that are hot at the top and cold at the bottom, of some radiators never warming while others are fine, and of boilers that bang or kettle when they fire. It also shortens the life of pumps, valves and heat exchangers, which is why manufacturers require systems to be cleaned when a new boiler is fitted.
Signs your system needs flushing
- Radiators cold at the bottom and hot at the top
- Some radiators never getting properly warm while others are fine
- Black, cloudy or gritty water when you bleed a radiator
- Banging, kettling or rumbling from the boiler when it fires
- Repeated pump failures or boiler lockouts
- Heating taking noticeably longer to warm the house than it used to
Power flush or MagnaCleanse?
A power flush is the more thorough option: water and cleaning chemicals are driven through the system at high velocity in both directions, radiator by radiator, until the water runs clear. It takes most of a working day and suits systems with genuine, widespread sludge build-up.
A MagnaCleanse is a faster magnetic clean that circulates the system through a powerful magnetic filter to capture iron oxide. It is less disruptive and less expensive, and suits moderately dirty systems or preventative cleaning. Our engineer will check radiators individually and look at the system water before recommending one over the other.
When flushing is not the answer
Not every cold radiator is caused by sludge. Trapped air, an unbalanced system, a stuck thermostatic valve or a failing pump all produce similar symptoms and none of them are fixed by flushing. We will rule those out first rather than sell you a flush you do not need.
Flushing with a new boiler
Most boiler manufacturers require the heating system to be cleaned and a system filter fitted when a new boiler is installed, and warranties commonly depend on it. Fitting a new heat exchanger to a system full of old sludge is the quickest way to block it. A system filter can be fitted alongside a MagnaCleanse from £150.
How charging works
Power flushing is £550 and MagnaCleanse is £400, both covering up to ten radiators with £40 per additional radiator. All prices exclude VAT. These are fixed prices rather than hourly work, because time on site varies with how contaminated the system turns out to be. Full current rates are on /our-rates.
After the flush
The system is refilled with clean water and a corrosion inhibitor is added. Keeping the inhibitor topped up at each annual service and having a magnetic system filter fitted is what stops sludge rebuilding and needing the same job again in a few years.
