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What are magnetic filters – and do I need one for my boiler?

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What are magnetic filters – and do I need one for my boiler?

The principle behind magnetic filters is very straightforward, and is about keeping your heating working efficiently. 

The steel in your radiators will, over time, corrode and combine with the water in the system to form a sludge. Such sludge can accumulate in the radiators which can reduce the free flow of hot water around the system.

Since the sludge is metallic, a sufficiently strong magnet will attract it and can therefore help to filter it out of the system.

Keeping sludge out of the system will have a number of benefits, mainly:

  • Lower heating bills
  • More efficient heat distribution
  • Less likelihood of breakdown
  • Reduced environmental impact

How do you know if your system has a sludge problem? Over time, you may begin to notice a number of symptoms. These may include increased noise levels from radiators and pipework, the radiators being slow to heat up and struggling to get to full temperature or you may notice ‘cold spots’ in parts of the radiators, and potentially the boiler regularly shutting down. At that point, before getting any sort of filter fitted, you might first need to get your system properly flushed, an extensive process that can take the best part of a day (so get it done before the cold weather arrives!). We would generally try fitting the filter first and only go for the powerflush as a last resort. 

Magnetic filters are relatively new, and it’s certainly not the case that your system must have one. You should already have a corrosion inhibitor in the water which will help reduce the problem. It’s also worth noting that metallic corrosion isn’t the only possible cause of sludge in your system, and a magnetic filter will have no effect on sludge that doesn’t have the metallic component.

Nevertheless, magnetic filters are generally low-priced additional components in the fight to keep your heating system well-regulated and reliable. The sludge that they collect can be removed on an occasional basis by a heating engineer – the easiest thing to do is to ask your engineer to remove it when carrying out your annual service.

Want to know if your system would benefit from having a magnetic filter installed? Ask your heating engineer to advise. 

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