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Extend your boiler’s life with a magnetic filter

Which? Trusted trader, Tom Sullivan, from Active Plumbing and Heating Solutions, explains why fitting a magnetic filter can prevent a boiler breakdown and save money.

What is a magnetic filter?

A magnetic filter is device that helps collect the sludge that can build up in a central heating system.

Much of the sludge is made up of rust particles that have corroded and come away from inside pipes or radiators. A magnetic filter is made up of a large magnet that attracts these particles, and then filters them out of the system. This helps prevent blockages and keeps the water flowing through the central heating system.

If you’d like to find out more about fitting a magnetic filter, you can find a Which? Trusted Traders endorsed central-heating engineer in your area.

Why would my heating system need a magnetic filter?

The iron and steel components in central heating systems are vulnerable to corrosion and rusting. This produces a sludge which can block different parts of the system, principally the boiler heat exchanger, pump or the radiators. 

Old, cast iron pipes were usually a few centimetres in diameter but more modern pipework tends to be narrower, making blockages even 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 or replace the heat exchanger – both costly jobs.

A magnetic filter can help avoid these blockages and keep the system running freely by trapping any sludge before it reaches the boiler. A powerful magnet collects the debris, preventing it from damaging the boiler.

Some of these devices 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. This means that it’s not always practical to install a magnetic filter – if the boiler is inside a small cupboard, for example.

How do you maintain a magnetic filter?

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.

Can a boiler inhibitor fluid prevent blockages?

Another method of preventing sludge build-up is adding corrosion inhibitor fluid to the central heating system. Maintaining the correct dose of inhibitor is an important part of caring for your boiler and some manufacturers require evidence of this to keep any warranty valid.

Your central-heating engineer can check the levels during your boiler’s annual service.

A magnetic filter works alongside the corrosion inhibitor fluid to help maintain your central-heating system’s effectiveness. A belt and braces approach is going to be more effective than using one and not the other.

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