Power Flushing

It's a process that forces water and a cleaning chemical through the heating system at a high flow rate and low pressure, dislodging sludge and debris from radiators and pipework so it can be flushed out, radiator by radiator.

Bleeding removes trapped air, usually indicated by warmth at the bottom and coolness at the top. Sludge does the opposite — cold at the bottom, warm at the top. If bleeding a radiator doesn't fix a cold patch, or the water that comes out is black and gritty, flushing is the more likely answer.

Not on its own — pressure loss is usually caused by a leak or a faulty component such as an expansion vessel or pressure relief valve, not by sludge. We'd diagnose the actual cause of pressure loss before considering whether a flush is also needed.

It depends on how fouled the system is. A chemical flush circulated for a period can be sufficient for lightly affected systems, while heavier sludge generally needs the higher flow rate of a power flush to shift it effectively.

Typically as part of an annual service, though a heavily sludged system may need it checked sooner after a flush while any remaining debris settles out. We check the filter each time we service the system.

It can, if pipework or radiators are already badly corroded and structurally weak — the flushing process can find a weak point that was previously being held together by the sludge inside it. We inspect the system's condition before recommending a full power flush.

In most cases, yes. Manufacturers generally require the existing system to be flushed clean before a new boiler is connected, since sludge from the old system can quickly damage a new heat exchanger.

A power flush treats the whole system at once using a dedicated pump. Mains-pressure jet flushing targets individual radiators using mains water pressure and is typically used where one or two radiators remain badly blocked after a general power flush.