Every new boiler quote you get in Lancashire now includes a magnetic filter — usually a MagnaClean Professional 2, an Adey MagnaClean, or a Fernox TF1. Cost on the invoice: £100–£170 fitted.
Customers ask us all the time: “Is this a genuine bit of kit, or is it the new way for installers to bump the price?”
Honest answer after fitting hundreds across Burnley, Blackburn, Preston and the rest of East Lancashire: it's the single best £150 you can spend on a new boiler. Here's why — and why every Gas Tech install includes one as standard, not as an upsell.
What a magnetic filter actually does
Central heating systems generate magnetite sludge — black, gritty iron-oxide particles produced when warm water meets steel radiators. Even a brand new system starts producing it the day you turn it on.
Without a filter, that magnetite circulates through your boiler thousands of times a year. The worst place it ends up: inside the heat exchanger — a fine network of microchannels where even a tiny grit deposit causes:
- Reduced flow → kettling, banging noises, cold spots
- Hot-spots → premature heat exchanger failure (£400–£900 to replace)
- Pump strain → premature pump failure (£250–£400)
- Boiler running 5–15% less efficient → £80–£150/year wasted on gas
A magnetic filter sits on the return pipe to the boiler. Its central magnetic core catches 99% of the magnetite before it can re-enter the boiler. You clean it out once a year at the annual service — takes about 5 minutes.
What does Worcester Bosch / Baxi / Vaillant actually say?
This is the bit installers don't always make clear:
- Worcester Bosch: requires a system filter to be fitted for the extended warranty (up to 12 years on Greenstar 8000) to be valid. No filter, no extended warranty.
- Baxi: requires a system filter for the 10-year Platinum Promise warranty.
- Vaillant: requires a system filter for the 10-year ecoTEC Plus warranty.
- Ideal: requires a system filter for the 10-year Logic Max warranty.
So on every modern UK boiler with an extended warranty, a magnetic filter isn't optional. If your installer is quoting without one to make their price look cheaper, your warranty is technically invalid from day one.
The three main filter brands — which is best?
1. MagnaClean Professional 2 (Adey) — the market leader
The original and most-fitted UK magnetic filter. Twin-magnet core, transparent body so you can see the dirt collected, full-bore valves for fast servicing. Our default fit. Cost in the install quote: around £140–£160.
2. Fernox TF1 Total Filter — strongest case for hard-water Lancashire
Adds a chemical dosing port to the standard magnetic filter — so the annual service includes a top-up of Fernox F1 inhibitor (the chemical that prevents corrosion in the first place). For homes in hard-water areas like Nelson, Colne or Padiham, this is the smarter buy. Cost: around £160–£180.
3. Spirotech MagnaBooster / Sentinel Eliminator — system-spec filters
Excellent build quality, popular on larger system boiler installs and unvented cylinder setups. Slightly bulkier — needs more clearance. Cost: around £150–£170.
All three will keep your warranty valid. The Worcester Bosch warranty paperwork specifically lists Adey, Fernox and Sentinel as approved brands.
Does the filter need servicing?
Yes — once a year, alongside the annual boiler service. The engineer:
- Closes the two isolation valves
- Drops a magnetic core into the canister to release the trapped sludge
- Drains the canister into a jug (you'll see why this matters in a minute)
- Rinses, refits, opens valves, tops up pressure
What comes out of an unserviced filter at year 5 is genuinely shocking — usually 50–100ml of pure black magnetite paste. That's what would have been inside your heat exchanger if the filter wasn't there.
The cost-benefit honest version
Take a typical 12-year Worcester Bosch Greenstar 8000 install in Burnley:
- Filter cost: ~£150 (fitted, included in the install)
- Heat exchanger replacement avoided over 12 years: ~£700
- Pump replacement avoided: ~£300
- Efficiency savings (5% gas reduction × £900/year average bill × 12 years): ~£540
- Warranty value preserved: the £700–£2,000 worth of free repairs you keep access to
So a £150 upfront cost vs roughly £1,500+ of value over the life of the boiler. Every Lancashire install we do includes one as standard. We don't bill it as an “extra”.
What if you have an old boiler without a filter?
You can have one retrofitted — usually £150–£250 to supply and fit on a return pipe near the boiler. The engineer will also do a quick chemical hot flush or recommend a full powerflush if the system is heavily sludged, otherwise you're just chasing existing sludge around with a brand-new filter.
For boilers over 10 years old without one, it's usually worth replacing the boiler entirely — see our 2025 boiler replacement cost guide for honest pricing.
The bottom line
A magnetic filter is not an upsell — it's a basic requirement of every modern UK boiler warranty, and the single most cost-effective bit of kit you can fit to extend boiler life. If your quote leaves it out, you're looking at a cheaper headline price and a more expensive 5-year reality.
Every Gas Tech install across Burnley, Blackburn, Preston, Nelson, Colne, Accrington and the rest of Lancashire includes a MagnaClean Professional 2 (or Fernox TF1 in harder-water postcodes) as standard. The warranty is registered with the filter fitted, you keep the paperwork, and the annual service includes filter cleaning at no extra charge.
Call 01282 914 044 or request a fixed-price quote — and check ours against any “cheaper” quotes to see which line items they've left out.