26 Oct 2017

You may have seen or heard that most heating systems now require a magnetic filter to be fitted. The are usually added on new boiler installs or systems that are less than 5-6 years old.

In this short blog post we will explain what the magnetic filter is and how it works on the newer heating systems installed today.

What is a Magnetic Filter?

A Magnetic Filter is a small plastic filter with a small magnet fitted to the middle of the plastic housing. It is fitted usually to the return pipe into the boiler and it used to help filter out any magnetic material that could be in the system and prevent it returning into the boiler. Newer heating system (paticularly combi systems) can have thinner pipes in the heat exchanger so anything in the system can cause a blockage a lot easier that the older system, the reason for this design is to increase the transfer of heat.

How does it work?

Magnetic filters work by passing the water from the system through the plastic reservoir and attracting any ferrous materials that could be in the system, This then stops any large deposits of debris entering the boiler itself and damaging any components, it can also help prevent any blockages that could occur in the heat exchanger due to the reduced amount of debris in the system. The ferrous material can come from the inside of the radiators, small amounts of metal that break off are due to oxidisation of the metal. The magnet that is inside the filters is also east for a technician to check to see if it is still working and picking up magnetic material, the magnet is easily detached from the plastic housing for inspection. It is also possible for the homeowner to also check this magnet but guidance or a service from a qualified technician is always advised as a first step.


Magnetic filters are something that can greatly help increase the lifetime of a boiler system, They prevent metal deposits in the system from getting into the heat exchanger and causing blockages or damage to the component. They are easily checked by technicians during routine services and specific call outs. Some boiler manufacturers warranties now state that a filter needs to be fitted to the system so they are slowly becoming standard for installs.

We also advise that if you are thinking of having a filter fitted to the system that you have the system power-flushed as well as this can deal with majority of the debris and sludge in the system before the filter has to take over.

I hope this blog post was informative and if there is anything that can be changed or added please let us know in the comments section. If you are looking to have a filter fitted or wish to talk to someone regarding it please contact us via our contact formĀ . We could also see if you qualify for a free boiler replacement.

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