The Homeowner's Guide to Magnetic Filters
A magnetic filter is the best £149 you'll ever spend on your heating system. Here's why every boiler needs one.
Iron oxide sludge — sometimes called "magnetite" — is the single biggest killer of boilers in the UK. It forms naturally in central heating systems as iron and steel components corrode slightly, and it accumulates in the heat exchanger causing overheating, inefficiency, and eventually catastrophic failure.
What a magnetic filter does
A magnetic filter (the most popular brands being Adey MagnaClean and Fernox TF1) attaches to the return pipe near the boiler. A powerful permanent magnet inside the filter body captures the iron oxide particles before they reach the heat exchanger, collecting them on the magnet where they can be periodically cleaned off by the engineer during annual servicing.
Why it matters for your warranty
Most major boiler manufacturers now specifically require a magnetic filter to be fitted for the full warranty to be honoured. Worcester Bosch, Vaillant, and Baxi all state in their warranty terms that sludge damage to a heat exchanger is not covered unless a filter was fitted. A single heat exchanger replacement costs £300–£600.
What does it cost?
An Adey MagnaClean Professional 2 fitted by our engineers: £149 + VAT. We fit one on every new boiler installation as standard — it's included in our installation price.
Do I need one if I already have a filter?
If you have an older filter, have it inspected at your annual service. Some older filters use mesh rather than magnets and are significantly less effective. We'll advise whether a replacement is worthwhile.
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