Power Flushing FAQs
Common questions about power flushing your central heating system.
What are the signs that I need a power flush?
Common signs include cold spots on radiators (particularly at the bottom), some radiators not heating up while others are hot, discoloured water when bleeding radiators, frequent boiler breakdowns, the system taking a long time to heat up, and noisy radiators or pipework. If your system is over 5 years old without treatment, a professional flush is worth considering.
How long does a power flush take?
A power flush typically takes between 6 and 10 hours depending on the size of your system and the severity of the contamination. Very large systems or severely sludged systems may take longer. We'll give you an estimated duration when we assess your system.
How much does a power flush cost?
Power flush costs depend on the size of your system (number of radiators). Typical prices range from £400 to £700 for a standard domestic system. We include the addition of corrosion inhibitor in our price. Call us on 01483 676108 for a specific quote based on your system.
How often should a central heating system be power flushed?
There's no fixed rule, but most engineers recommend a power flush every 5–6 years, or whenever symptoms of sludge build-up appear. The frequency depends on the age of your system, the quality of the original installation, whether inhibitor has been maintained, and whether a system filter is fitted.
Do I need a power flush before a new boiler?
Yes, it is strongly recommended (and often required by boiler manufacturers) to flush the system before installing a new boiler. Installing a new boiler onto a sludge-contaminated system can dramatically shorten the boiler's life, void the warranty, and cause premature failure of the heat exchanger. We typically carry out a Magna Cleanse as part of every new boiler installation.
What is a system inhibitor and why is it added?
Central heating inhibitor is a chemical added to the system water to prevent internal corrosion and scale build-up. It protects metal components including the boiler's heat exchanger, pump, and radiators. Inhibitor should be checked annually during your boiler service and topped up as needed. It's always added after a power flush to protect the newly cleaned system.
What causes sludge to build up in a heating system?
Sludge (technically magnetite) forms when oxygen in the system water reacts with steel radiators, causing them to corrode from the inside. Over time, this corrosion product settles in radiators and pipework, reducing heat output and damaging the boiler pump and heat exchanger. Poor initial commissioning, lack of inhibitor, and the absence of a system filter all accelerate sludge build-up.
What is a magnetic system filter and do I need one?
A magnetic system filter (such as a Magnaclean or Adey MagnaClean) is fitted to the heating circuit and captures metallic sludge particles before they can reach the boiler. Most boiler manufacturers now require a filter to be fitted as a condition of their warranty. After a power flush, fitting a filter dramatically slows the return of contamination. We fit filters on all new boiler installations as standard.
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