One of the most common problems we see, especially with older systems, is parts such as heat exchangers, pumps and radiator pipes becoming blocked. When these blockages are only partial, this can make your system much less efficient. This means you have to burn more fuel to achieve a comfortable temperature and so your heating bills go up. Even worse, if a part becomes totally blocked, this can lead to your boiler breaking down costing you a lot of money to replace. Magnetic filters are one way to prevent blockages, but whether you need one depends on several factors.
Sludge
Blockages in central heating systems are commonly caused by ‘sludge’. Sludge is a thick mixture of various metal oxides produced by water in your central heating reacting with metal components and corroding them. Most of this sludge is in fact made up iron oxide (more commonly called rust) and this is where magnetic filtration can help. Because iron is attracted to magnets, a magnetic filter attached to your central heating can collect any iron oxide travelling around your system and remove it. This prevents the build-up of sludge and protects your boiler and other parts of your system.
Corrosion inhibitor
One alternative to magnetic filtering is to dose your central heating system with corrosion inhibitor. In theory this should help prevent corrosion, meaning there would be no metal oxides in your system that would need removing. However, this is not always entirely reliable and some types of system are more at risk than others, so even where corrosion inhibitor is used, a magnetic filter may still be a good idea.
When to use magnetic filtering
Many modern boilers have heat exchangers with very narrow tubes or closely spaced plates which makes them more efficient, but also leaves them vulnerable to blockages from even a relatively small amount of sludge. In these cases it is often a wise precaution to have a magnetic filter installed to offer your boiler the best possible protection and minimise the risk of future problems.
If you’ve suffered a boiler breakdown in Bristol, our engineers have the knowledge and experience to identify the issue and suggest an appropriate solution. We always take care to identify any underlying problems and take action to make sure you won’t keep getting hit by the same dilemma.
Unit 2 Septimus Buildings 
Thanks for that useful advice about magnetic filters. Is it necessary to have a complete purge/flush of the system before fitting the magnetic filter?. Mine is an old (40 yrs) copper pipe steel rad system with a Bosch vented boiler. I have emptied the system several times including recent years and found the drain water clear. We are a soft water area.
Please comment.