Are magnetic filters worth it?

What is a magnetic filter?

As water passes through the metal pipes and radiators in your central heating system, rust can form. This rust can then break off and, when combined with other debris and dirt, it can form a mud-like substance often referred to as sludge. This sludge travels through your central heating system and can start to settle in certain places, leading to a range of potential problems. 

For example, when it builds up at the bottom of radiators, it can cause cold spots, meaning your heating won’t function as efficiently as it should. The substance can also start to clog up components within your boiler, such as the pump or heat exchanger. This could result in breakdowns and mean you need to have parts of the appliance replaced.

Magnetic filters are designed to catch this sludge and therefore prevent these problems. The fact that they are magnetic means they are effective at attracting and removing the corroded iron and steel material within the sludge. Designs that include a gravity filter also remove non-ferrous debris.

Bear in mind that if your heating system is heavily blocked by sludge, fitting a magnetic filter won’t be enough to clean it. You’ll need to powerflush your system first.

Do I need a magnetic filter for central heating?

If your radiators tend to stay cool at the bottom but they get hot at the top, this could be a warning sign that there is a sludge build-up. 

Having to bleed your radiators regularly to ensure they get hot at the top is another giveaway. Your boiler making strange gurgling or banging noises can also point to a sludge problem, as can pump leaks or failures. When parts are removed from your boiler, check them to see if they are full of dirt. If they are, this shows that there is sludge in the system.

If you don’t tackle this problem, your heating system will become less and less efficient, meaning you end up paying more in energy bills and your carbon footprint increases. You also run the risk of needing potentially expensive boiler repairs, and the lifespan of this appliance may be reduced. Your boiler warranty could be affected too.

Also, if your heating system doesn’t have a magnetic filter, you might need to arrange power flushes from time to time to remove the debris. This process can be time consuming and costly.

Where to fit a magnetic filter

Magnetic filters are fixed to the pipe that returns water to the boiler after it has travelled around the central heating system. They are most commonly added to boilers during installation. The filters can sometimes be fitted onto existing systems, but depending on the location of the boiler, this is not always feasible.

If you’re not sure if there’s space near your boiler to add a magnetic filter to the return pipe, you can contact a central heating engineer. This expert will be able to tell you if the work is possible and whether it will benefit your central heating system.   

How to clean a magnetic filter on a boiler

Just like other parts of your heating setup, a magnetic filter must be maintained in order to carry on working properly. It’s generally recommended to get this piece of equipment cleaned every year or so to remove the debris that it has caught. The easiest way to do this is to ask your heating engineer to inspect and clean the filter when they do your annual boiler service. As long as it’s easy to access, this shouldn’t add much time or cost to the service.

Keeping up with this maintenance will mean your magnetic filter continues to help protect your boiler and central heating system from a build-up of sludge well into the future.

If you’d like further information or advice on this topic, or on any other issue relating to a Viessmann boiler, don’t hesitate to contact our UK-based customer service team.