Central Heating

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 are my radiators cold?

Cold radiators are usually a consequence of air being trapped inside the radiator. Simply bleed the radiator and the problem should be resolved. Sludge buildup can also cause differences in the top and bottom of your radiator and impact its efficiency. 

How do I know if I've got sludge in my central heating system?

If you notice your radiators are hot at the top but cold at the bottom, or need to bleed your radiators more often, then you may have sludge built up in your system. 

Does my boiler filter need cleaning?

Your filter should be cleaned during your boiler’s annual service. This will prevent sludge building up in your system. Some filters come with an app that can warn you when they filter needs to be cleaned, so that you can arrange for your installer to visit before it gets too full.

What is central heating sludge?

Central heating sludge is a substance that builds up in central heating pipes as a result of rusted and dissolved metal settling in the system.

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