Power flushing — do you actually need it?
Check the steps below first — if you're not confident, get it fixed safely today.
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Most likely cause & what to check
Power flushing forces pressurised water mixed with chemicals through your heating system to remove sludge (magnetite), limescale, and rust. It's genuinely needed in some cases — but also oversold.
Signs you may need it: cold patches at the bottom of radiators (classic sludge symptom), dark brown/black water when you bleed radiators, repeatedly blocked pump, or the system taking a very long time to heat up.
Get a free check first: bleed a radiator and look at the water. If it's clear, power flushing is unlikely necessary. If it's very dark and dirty, there's significant sludge.
A good engineer will also use a magnetic filter (MagnaClean or similar) reading to test sludge levels, and may do a flow test to confirm the pump is struggling.
For a new boiler installation onto an old system, a power flush or chemical flush is strongly recommended — many manufacturers require it to maintain warranty.
Chemical flushing is a cheaper alternative (£100–£200): corrosion inhibitor and cleaner are added and left to circulate. Less thorough than power flushing but adequate for mild cases.
After any flush, a magnetic system filter should be fitted to catch future sludge. Without one, the system will sludge up again in a few years. The filter needs cleaning annually at service.
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