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

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.

What is central heating sludge?

Sludge or magnetite if left to build up, can damage the boiler and the heating system. Find out everything you need to know about Sludge here...

What is a magnetic boiler filter?

Find out everything you need to know about the magnetic boiler filter, how they function, why should the filter be fitted, and how to look after them.

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