Boilers & Heating
Magnetic filter installation
TL;DR
A magnetic system filter fitted on the return pipe to the boiler is the single best £180-£260 you can spend on a heating system. It catches the black magnetite sludge before it reaches the boiler's heat exchanger, doubles the effective life of the boiler, and is a warranty condition on most new installs (Worcester, Vaillant, Ideal).
Central heating sludge is a fact of life. Iron radiators, copper pipe and steel components corrode very slowly and produce iron oxide — magnetite — which circulates as a fine black powder in the system water. Without a filter, that magnetite ends up in the boiler's heat exchanger where it insulates the flame from the water, causes kettling, and eventually blocks the pump. Fit a magnetic filter and 90% of that debris is captured harmlessly on the return, where it can be flushed out in 30 seconds during the annual service.
This page covers which filter to buy, how it wires into your system, and why it's now a warranty condition on almost every new boiler in the UK.
Fixed £50 diagnostic
Flat fee. No hourly meter running.
Fair quote or refund
Transparent pricing — refunded if we don't fix it.
Vetted UK engineers
DBS-checked, insured, real reviews.
AI-triaged in seconds
KJ chats first so the right engineer arrives.
Which magnetic filter is best?
The four we fit as standard, all excellent, all with 10-year+ warranties:
- Adey MagnaClean Pro 2: highest magnetic capture, dual-flow, cleanest to service — our default fit
- Fernox TF1 Omega+: slim body for tight cupboards, excellent chemical dosing port
- Adey Micro 2: budget option, same capture, smaller body
- Spirotech MB3: combined magnetic + dirt separator, best for open-vented systems
Where is the filter installed?
On the central heating return pipe, immediately before it enters the boiler — that's where the manufacturer instructions require it and it's where the pipe run makes most sense. On combi boilers this is usually a 22mm pipe under the boiler; on system boilers it's often in the airing cupboard. Fitting takes 45-90 minutes including draining the affected section, cutting-in the isolating valves, mounting the filter body and refilling with inhibitor.
How does it actually work?
System water flows through a chamber containing a powerful neodymium magnet. Ferrous debris (magnetite sludge) is drawn onto the magnet and held there. Non-ferrous debris (limescale, copper flakes) drops out in the sedimentation chamber below. When you (or we) service it, the magnet lifts out and 30 seconds under a running tap flushes the whole thing clean.
Is a magnetic filter a warranty condition?
Yes for most brands, yes for the longer warranty periods. Worcester Bosch, Vaillant, Ideal and Baxi all require a system filter to unlock their extended warranties (typically 10-12 years). Fit the boiler without one and you're usually back to the base 2-3 year warranty. It's the cheapest way to double your boiler's guarantee.
Can a filter replace a power flush?
Not on a system that's already silted — you need to power flush first, then fit the filter to keep it clean afterwards. But on a new system, a filter fitted from day one prevents the sludge build-up that leads to power flushes being needed a decade later. Prevention is cheaper than cure.
Typical prices
Real-world ranges from recent Northwest jobs. Your final price is confirmed in writing before any work starts.
| Item | Typical price | Notes |
|---|---|---|
| Adey MagnaClean Pro 2 — supplied & fitted | 220 – 280 | Default fit, 22mm horizontal or vertical |
| Fernox TF1 Omega+ — supplied & fitted | 200 – 260 | Slim body for tight cupboards |
| Adey Micro 2 — supplied & fitted | 180 – 230 | Budget option, smaller body |
| Spirotech MB3 — supplied & fitted | 260 – 320 | Combined magnetic + dirt separator |
| Filter fit during a new boiler install | 140 – 180 | Bundled cost, isolation valves included |
| Filter fit during power flush | 150 – 200 | System already drained down |
| Filter service (during annual boiler service) | included | 30-second magnet clean + dose check |
| Chemical dose top-up (Fernox F1) | 35 – 55 | Through the filter's dosing port |
Which brand should you fit?
We fit Adey MagnaClean Pro 2 as our default (best capture, cleanest to service, 10-year manufacturer warranty), plus Fernox TF1, Adey Micro 2 and Spirotech MB3 depending on the pipe run and boiler location. We're independent — no manufacturer commissions. We install and service Worcester Bosch, Vaillant, Ideal, Baxi, Viessmann and Alpha — none of them pay us commission and we don't push a "boiler of the month".
Our promise on this job
Flat £50 diagnostic — deducted in full from any work booked. Fair, transparent quote before we start. If we can't fix the fault we diagnosed, we refund the diagnostic. All gas work is signed off by a Gas Safe registered engineer.
Talk to KJ about magnetic filter installation
Real triage in seconds. £50 diagnostic visit — refunded if we don't fix it.