What is a magnetic boiler filter?

The water in your central heating system flows from your boiler, where it is heated up, around all your radiators and then back to the boiler to be reheated and circulate again.


A magnetic boiler filter is a small device that is installed into the pipework close to where the water goes back into your boiler.


As the water passes through the filter, a strong magnet attracts any fragments of rust and other magnetic debris (called magnetite or iron oxide 'sludge') and stops it from entering the boiler and causing damage or blockages. You will need to get the filter cleaned at the same time as your annual service to remove all the debris that has accumulated in it.


As well as the potential to damage your boiler, sludge in the radiators will cause cold patches at the bottom, so your heating will have to work harder to reach your set temperature, in turn increasing your fuel bill. Read more about why it is important to look after the water in your heating system.

Related FAQs

Does my boiler filter need cleaning?

Ask your installer to clean your filter while carrying out your annual boiler service. Read more to find out why this is important...

Do I have to have a magnetic boiler filter installed?

Fitting a filter is considered best practice when installing a new boiler. The installer must carry out the following steps when a new boiler is fitted...

Why should I have a filter fitted?

Many boiler breakdowns occur are due to sludge in the heating system. Find out the many benefits of fitting a magnetic filter & how it can save you money.

Why should I get the water in my central heating system cleaned?

If Boiler breaks down due of sludge in the system, the repair work is not covered by the Boiler warranty & can lead to expensive repair bills. Read more...

Why are my radiators cold?

Not sure why your radiators cold at the top or bottom? Find out the reasons and simple solution to resolve this.

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