What a magnetic filter does
A magnetic filter is fitted to the heating pipework near the boiler. As water circulates, it traps the fine black iron oxide sludge (magnetite) that forms inside radiators and pipes, before it can reach the boiler.
Why it matters after a power flush
A power flush removes the existing sludge. Without a filter, the system will slowly start to collect new sludge, because the same corrosion process continues. The filter catches it as it forms, so the system stays cleaner for longer. Our guide to what a power flush is explains the process.
Warranties
Some boiler manufacturers expect a filter to be fitted, particularly with a new boiler, so it’s worth checking your terms. See boiler warranties explained.
Keeping it working
A filter only works while it has room to hold sludge. It needs cleaning periodically, which is usually done at your annual service — see what’s included in a boiler service.
Do you actually need a power flush?
If your radiators are cold at the bottom or the boiler is noisy, sludge could be the cause. Read do you need a power flush? to check the signs.
Our power flush includes a magnetic filter, so your system stays clean. South Manchester and Cheshire.
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