What Is a Magnetic Filter?
A magnetic filter — sometimes called a boiler filter or system filter — is a device fitted to the return pipe of your central heating system, just before the boiler. It contains a powerful magnet that captures iron oxide particles (sludge and magnetite) as they circulate through the system, preventing them from entering the boiler's heat exchanger.
Why Does Sludge Form?
All central heating systems produce iron oxide over time as water reacts with steel pipework and radiators. This black, gritty sludge circulates in the heating water and gradually:
What Does a Magnetic Filter Do?
The magnetic filter captures these particles before they reach the boiler. The collected sludge is retained inside the filter body and removed when the filter is cleaned — typically during each annual service visit.
Popular Brands
The most well-known magnetic filters are the Magnaclean (Adey) range and the Fernox TF1. Both are widely used by heating engineers throughout the UK and are recommended by most major boiler manufacturers. Some boiler warranties now require a magnetic filter to be fitted.
Cost and Installation
A quality magnetic filter costs around £50–£100. Installation takes approximately 30–45 minutes and involves isolating the return pipe, fitting the filter body, and refilling and bleeding the system. The filter should be cleaned at every annual service.
Should You Have One Fitted?
Yes — particularly if your system is over five years old, if you've never had a power flush, or if you're fitting a new boiler. The protection they provide is disproportionate to their relatively modest cost.
Halo Heating supplies and fits magnetic filters across Surrey as part of new boiler installations and standalone visits. Call 01483 676108.
Need Professional Help?
Our Gas Safe registered engineers cover Surrey and surrounding areas. Call for a free quote or to book an engineer.
Call 01483 676108