Magnetic Filters, what do they do?


A magnetic filter is device that collects the sludge circulating in a central heating system before it can damage your boiler.

Why does my boiler break down?

The iron and steel components in central heating systems are vulnerable to corrosion. This produces a sludge which can block a boiler heat exchanger, boiler pump, radiators and valves.

Old, cast iron pipes were a few centimetres in diameter but those on modern boilers (installed in the last ten or so years) tend to be narrower, making a blockage more likely.

A blocked boiler will often overheat, causing the system to shut down. To remove a blockage, a boiler engineer may have to power flush your central heating system, replace the heat exchanger or fit a new pump – all are costly jobs that might be avoided with a magnetic filter.

How can a boiler blockage be avoided?

A magnetic filter is a simple device which traps the sludge that is created before it reaches the boiler. A powerful magnet collects the debris, preventing it from damaging the boiler.

Some of these devices such as BoilerMag by Eclipse also include a filter which gathers non-magnetic deposits from corrosion of copper, zinc or aluminium central heating system components.


How can I install a magnetic filter?

If you’re having a new boiler installed, your boiler engineer may recommend that a magnetic filter is also fitted. Some boiler manufacturers will extend the boiler warranty if a magnetic filter is installed.

It’s also possible to add a magnetic filter to an existing system. The unit can be quite bulky and is fitted close to the boiler itself. So, sometimes a magnetic filter can’t be installed – if the boiler is inside a small cupboard, for example.

How is a magnetic filter maintained?

The build-up of sludge inside the filter must be removed from time to time. Boiler engineers will usually clean the filter as part of an annual boiler service. The unit can also be cleaned my the house holder quite easily, the engineer who installs the filer will demonstrate how to clean once installed.

Doesn’t a boiler inhibitor fluid prevent a blockage?

Corrosion inhibitor fluid can be added to the central heating system to prevent the production of sludge. Maintaining the correct dose of inhibitor is an important part of caring for your boiler (and is required by some manufacturers for the warranty to be valid) but installation of a magnetic filter is a good precautionary measure to take in conjunction with this.


Here’s a video from Adey Magnaclean Pro2 showing how a magnetic filter works.


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