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Are Magnetic Filters Worth it?

Witten by Bernard Morgan (Engineer) & Adam Apperley (Marketing). Published: December 11, 2023. Updated: March 15, 2024

Spirotech Magnetic Filter | BoilerhutThe purpose of a magnetic filter is to catch most of the sludge that circulates your central heating system.

If ignored, this mixture of metallic and non-metallic deposits can build up to the point where your radiators have cold patches, your boiler’s efficiency is drastically lowered, and your energy bills are raised.

Without a magnetic filter, you will experience these issues, and they will only get worse. A magnetic filter can help extend your boiler’s lifespan and reduce energy bills.

Why do I need a magnetic filter?

Having a magnetic filter installed has benefits that include:

  • Reduction of your annual energy bills by up to 6% (3-bedroom example)
  • Improved boiler efficiency
  • Reduced likelihood of boiler repair
  • Increased boiler lifespan
  • Reduced carbon footprint

Over time, your central heating system can fall victim to corrosion and rust. When this occurs, tiny particles from the deposits eventually collect to form a dark sludge.

Sludge deposits make it difficult for your system to operate to its full potential, so a magnetic filter will be needed

Occasionally, this can also produce an unusual dark orange colour, which is a direct result of internal rusting that can sometimes occur. The sludge is left to either sit at the bottom of your radiators or clog up your pipework and other areas of your heating system.

Sludge deposits cause cold patches to form at the bottom of your radiator

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Side Effects

Side effects of not having a magnetic filter installed

Nobody wants a broken boiler, but these things can happen they’re not taken care of!

If you don’t get this sludge removed, there can be some troublesome side effects.

  • ‘Kettling’ noises coming from your boiler
  • Radiators not heating properly due to cold patches
  • An overheating boiler

A magnetic filter deals with this by collecting the dirt particles as they’re coming through the system. It holds onto them until it’s emptied – whether this is done every few months or during your annual service will depend on aspects like age and condition of the current system.

What happens if I don’t have a magnetic filter installed?

Suppose you choose not to have a magnetic filter installed. In that case, the most significant consequence is that you could invalidate your manufacturer’s warranty and your energy bills continue to rise. This is because your radiators are no longer able to heat at full capacity, due to the magnetic sludge in your system.

If the efficiency of your boiler is affected too much, you may have to consider a replacement. This can be scary, but the good news is that getting one fitted is extremely easy.

It’s clear at this point just how many benefits there are with having a magnetic filter installed. However, if you choose not to have one, be aware that magnetic sludge will still continue to form.

If your system is already filled with sludge, you’ll need one of three types of flush performed:

  • Chemical flush
  • Power flush
  • Advanced flush

All of these need to be carried out by a visiting professional and involves pumping chemicals through the pipes, radiators and boiler to get rid of any limescale or magnetic sludge deposits. This is a reasonably long process usually taking several hours, and is often the more expensive option.

When any of these are carried out, your system will need to be dosed with an inhibitor to keep the pH levels of the water reasonable. This slows and prevents the build-up of magnetite sludge once you’ve had your system cleaned. After this, simple water tests are a useful way of finding out if they’re successful.

If the damage is built up enough over time, the worst-case scenario is that your system will need to be replaced.

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Can I install one on the system I already have?

A magnetic filter will commonly be installed at the same time as a new boiler installation. However, it is still possible to have one fitted to an existing system though.

Do I need to clean my magnetic filter?

The frequency of how often you should monitor the sludge in your system filter can vary. However, the best practice is to check during the boiler’s annual service. When full of sludge, some magnetic filters can affect the performance of the system due to a reduced flow rate.

If you’re feeling unsure, it’s always best to have them professionally cleaned out. If you’ve recently had a power flush or you’re aware of sludge already sitting at the bottom of your radiators, you may find that the filter can pick up more during its first period of operation.

Once you’ve cleared out most of the sludge from your system, it doesn’t need to be emptied as often, and can be done during your annual boiler service.

Examples of magnetic filters

It pays to know about the brands that are currently available on the market. As much as we can learn about how magnetic filters actually work, the following list is a selection of some of the main brands available:

Spirotrap MB3

Manufacturer: Spirotech

Spirotech has a track record of designing and manufacturing excellent products in the central heating industry. Their magnetic filters are brass in construction and provide outstanding results for helping you clean out your system.

By learning from previous iterations of their ‘MB’ line, Spirotech has made several improvements to the filter design, making them a strong competitor.

How does it work?

The Spirotrap MB3 uses a removable magnet and spirotube element to make up its unique dual separation system. With this design, magnetic and non-magnetic particles are collected and filtered out, making your system a lot cleaner. The filter itself contains a unique magnetic field booster which extends the filter’s dirt collection capacity, meaning it can remove more dirt, more quickly.


  • 20-year guarantee
  • Magnet part boasts magnetic field booster technology
  • Easy installation
  • Duel action technology removes magnetic AND non-magnetic deposits
  • Increased flexibility on where filter can be positioned on pipework
  • Maintenance only takes a few seconds
  • Spirotrap also state that there is no flow loss on their filters

Magnaclean Atom

Manufacturer: Adey

Much like the previous filter, the Magnaclean Atom helps protect your central heating system from the negative effects of black iron oxide sludge. With a compact design, it can be installed in most areas, even if your boiler has already been fitted. It can also be fitted onto vertical or horizontal pipework and comes fully supplied ready to be installed on the day.


  • Carbon emissions are reduced
  • Save up to 6% on annual energy bills
  • Lifespan of heating system extended
  • Needs only 115mm to be installed even in the smallest of spaces

Fernox TF1 Compact Magnetic Filter

Manufacturer: Fernox

The TF1 Compact uses hydrocyclonic technology to pick up the mixture of metallic and non-metallic elements that make up the internal sludge in your radiator. It can be connected directly onto 22mm pipework and can be installed horizontally or vertically, allowing greater flexibility in positioning.


  • Ideal for areas with restricted space and access
  • Fast and easy to clean without having to dismantle your unit
  • Options of vertical or horizontal offer improved position flexibility
  • Doesn’t block or restrict flow of water
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Are magnetic filters worth it?

Full Magnetic Filter - Are Magnetic Filters Worth It? | BoilerhutYes. Considering the level of damage that sludge can cause to your central heating system, including your boiler, installing a magnetic filter is a no-brainer. Once you have it, you’ll be able to enjoy:

  • A clean heating system free of sludge and iron oxide deposits,
  • Potential reductions of your annual energy bills,
  • Extended boiler lifespan.

Here at Boilerhut, we install magnetic filters as standard for all boilers and new central heating installations. Not only do we think it’s a no-brainer for the lifespan of your system, but because we’re a Viessmann Premium Partner, we install them to ensure your warranty for the full 10 to 12 years.

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