Power Flush

You may need a power flush if you notice several of these:

• Radiators cold at the bottom or in the middle while the top is warm, on more than one radiator.
• Black or brown water when you bleed a radiator.
• Slow warm-up: The house takes longer to heat, or some rooms never get properly warm.
• A noisy boiler: Banging, gurgling or "kettling" as water boils in a restricted heat exchanger.
• Repeated faults: Failed pumps, blocked valves or boiler lockouts that keep coming back.
• A magnetic filter that fills up fast every time it is cleaned.
• A new boiler is planned: An old system should be cleaned before a new boiler goes on.

One cold radiator on its own may only need bleeding, a freed valve or a single radiator flush: see our radiator maintenance and repair service first. A banging boiler can also be caused by scale or a boiler fault, which our boiler repair service can check.

1. 1

   Check the system: we look at the radiators, valves, pipework and boiler, test the water and note any existing leaks or weak points.

2. 2

   Connect the pump: a power flushing unit is connected into the circuit, usually in place of the circulating pump or at a radiator.

3. 3

   Add the cleaner: a cleaning chemical is circulated to loosen sludge and scale.

4. 4

   Flush each radiator: radiators are isolated and flushed one at a time, with the flow reversed and the radiators agitated to dislodge debris.

5. 5

   Dump and rinse: the dirty water is sent to the drain while clean mains water is fed in, until the water runs clear. We compare the system water with the mains water to confirm it is clean.

6. 6

   Protect: the system is refilled, inhibitor is added, and a magnetic filter is fitted if there is not one already.

7. 7

   Recommission: we bleed the radiators, set the pressure, check for leaks and balance the system.

If the boiler itself needs any attention during the work, that is carried out by Gas Safe registered engineers, as the law requires.

A flush clears out the sludge; what stops it coming back is protection:

• Inhibitor: A chemical added to the heating water that slows the corrosion which creates sludge in the first place. Its level should be checked regularly, often at the annual service, and topped up when the system is drained.
• Magnetic filter: Fitted on the return pipe near the boiler, it catches magnetite as it circulates. It is cleaned out at each service.
• BS 7593: The British Standard code of practice for treating the water in domestic heating systems. It sets out cleaning, flushing and protecting the system, and boiler manufacturers commonly expect a system to be cleaned to it before a new boiler is fitted.

Keeping the inhibitor and filter in good order is part of our central heating system maintenance service.

A new boiler has a smaller, more efficient heat exchanger than most older boilers, and sludge from the old system can block it. That is why the system should be cleaned before or as the new boiler goes in, and a filter fitted. Depending on the state of the water, that means a chemical flush or a full power flush. We include it in the quote for our boiler replacement and boiler installation services.

Yes, when the signs are there. A clean system circulates freely, so radiators heat evenly and the boiler and pump are under less strain. It is not needed as a routine job on a system that is already clean, with good inhibitor levels and a working filter. If your water is clean when you bleed a radiator, we will tell you that a flush is not needed.