Magnetic Filter Installation — UK-Wide, Qualified & Priced Up Front
Magnetic system filters — handled UK-wide by qualified, insured local engineers, with the price agreed before work starts and honest advice on what your system actually needs.
What a magnetic filter does
Central heating water corrodes steel radiators from the inside, producing magnetite — the black sludge behind cold radiator bottoms, blocked pumps and failed heat exchangers. A magnetic filter fitted on the return pipe to the boiler captures that debris in a magnet-lined canister before it reaches the boiler's narrow waterways, and gets emptied at each annual service. It's a passive, no-moving-parts device: an hour to fit, decades of quiet protection, and the single most cost-effective hardware addition an unprotected system can receive.
The filter is also a diagnostic instrument: what comes out of it at each service tells the story of the system's water. A light dusting means the inhibitor is doing its job; a canister packed with black paste means active corrosion and a chemistry problem to fix. That feedback loop — filter catch checked annually, inhibitor topped to match — is how systems stay clean after a powerflush and why manufacturers increasingly expect a filter on new boiler installations.
Fitting, cost and when it's worth it
Supply and fit runs £120–£220 fixed depending on the filter model and pipework access, typically within the hour on accessible pipework near the boiler. Worth it when: the system lacks one (most pre-2010 installations), you've just had a powerflush or cleanse and want the results to last, or a new boiler is going onto an older system. Marginal when the system is new, clean, filtered already, or the pipework layout makes access disproportionate — in which case we'll say so rather than sell the fitting.
One honest caveat: a filter is protection, not treatment. Fitted to a badly sludged system without cleansing, it fills fast and the untreated water keeps corroding — the sequence that works is cleanse, inhibit, then filter. Fitted as part of that sequence, or onto a healthy system as insurance, it quietly earns its keep every winter and shows its work in the service engineer's hand once a year.
| Item | Guide |
|---|---|
| Typical price band | £120–£220 |
| Pricing basis | supplied and fitted, fixed price |
| Typical timescale | 1–2 hours |
| Funnel | Attendance and diagnosis |
| Credentials | Qualified heating engineer |
Frequently asked questions
Where does a magnetic filter go?
On the return pipework just before the boiler, so debris is caught before entering the boiler's heat exchanger. Fitting takes about an hour on accessible pipework, with the filter positioned so the canister can be opened for cleaning at each service.
Do magnetic filters really work?
Yes — magnetite is strongly magnetic and the capture is straightforward physics. The proof arrives at each annual service when the canister is opened. What a filter can't do is fix bad water chemistry; it partners with inhibitor, not replaces it.
How often should the filter be cleaned?
At every annual boiler service — it's a two-minute job for the engineer and doubles as a health check on the system water. A filter left unopened for years just becomes a full canister doing nothing.
Does a new boiler need a filter?
Manufacturers increasingly expect one and some tie warranty terms to system cleanliness. Every installation our network arranges includes a filter as standard; retrofitting one to an existing boiler is this page's fixed-price job.