A Magnetic Central Heating filter is a sealed filtration device containing a magnet that is fitted to the return leg of the central heating system next to the boiler. It is designed to remove debris from the central heating system. Reducing possible damage to the boiler and heat exchanger.
Sludge within the heating systems is ferrous in nature, containing steel or iron as a result of corrosion. This can be trapped by the magnetic filter, before entering and causing damage to the boiler.