Magnetic Filtration: What Is It And Do You Need It?

27 Apr. 2019

Written by Neil Marsh MCIPHE RP RHP EngTech

The purpose of magnetic filtration in wet central heating systems is to help remove magnetic particles that are mobile in the system water and reduce the associated problems from the accumulation of these particles … These particles mostly come from the corrosion of the radiators attached to the central heating system which typically are made of steel. Some older heat exchangers and steel pipework can also be responsible.

Do They Work?

It would be a lie to say that magnetic filtration does not offer any benefit. However, the benefits are often grossly overrated by the manufacturers (Adey, Fernox, Sentinel etc), and have now become part of a marketing wave by plumbing and heating companies using them increase profits when undertaking boiler installations/replacements, power flushing and maintenance work.

Sadly, there are a plethora of plumbing and heating companies pushing these products onto customers as an alternative to power flushing and/or as a much-needed product. The reality could not be any further away from the truth! These products are often sold as a solution to sludge within a central heating system when they are nothing more than a complementary measure when used correctly. In addition, these products are often poorly installed, and any benefits that could be gained from their use are often lost.

Cutting The Bull S**T!

Does a central heating system need a Magnetic Filtration? The answer is no!

Can they benefit a central heating system? When installed correctly they can, but the cost to benefit ratio needs to be considered.

Most magnetic filters are merely that, a magnet that will help filter magnetic debris. Some do incorporate filters for non-magnetic material. A magnetic filter without a physical filter will not protect a central heating system from other sediments that may be present that the magnet will not attract. Depending on what is causing the issues within the heating system (sludge, scale, other debris), the use of a magnetic filter could offer no benefit what so ever.

How Filters Work

Lets take a look at the market leaders premium filter, the Adey MagnaClean Professional 2:

Looks pretty convincing, yes?  Well let us go more in-depth about the filtration process:

Magnetic debris mostly comes from radiators and other ferrous components in the heating system following corrosion. Collecting this material does not address the cause, which is that water, oxygen and the steel in that radiators are made from (or cast iron in some older versions), is reacting and causing corrosion. Often fluxes and other residues from the installation are present in the system which can affect the PH of the central heating system water. Where this is the case, the rate of corrosion will be quicker. 

As corrosion breaks away from the components (flakes off) and makes its way into the central heating system water, it begins to circulate through the heating system due to the flow generated by the pump. However, as it is denser than water, it will collect in lower parts of the system and often this is long before it reaches any filter. It collects easily in areas where the flow is restricted, like the flow in heat exchangers, and also around components that also generate a magnetic field, like pumps and motorised valves, as well as the radiators and pipework.

Magnetic debris that is mobile in the water may be collected as it passes the magnet. However, only a small percentage will be picked up by the filter in reality. It needs to pass the magnet for this to happen if it happens at all. 

Filters vary in quality. The only filter we have found to be highly effective at collecting debris that passes it, is the Fernox Omega Filter, which is also made for Ideal and known as the Ideal System Filter. 

Magnetic filtration does not address the cause of corrosion, nor does it protect a central heating system from limescale and other debris that may have gotten in there during installation or from the mains water supply. Some filters may help collect non-magnetic filter material, however in our experience, unless there is a physical barrier for this sediment to get caught up in many of the “vortex” products will fail to filter smaller, lighter particles effectively.

Here are diagrams from the MangnaClean Professional 2 advising on the installation of the product:

The idea is that the return pipe after the last radiator on the circuit will have the most magnetic debris. Magnetic debris (and non-magnetic debris) mostly affects the system by reducing flow through the radiators, pipework and the boiler, as well as getting caught in the thermostatic radiator valves, pump and motorised valves causing faults in their operation. By failing to install the filter in position “A”, you are reducing the level of protection that the filter can give as the most contaminated water will pass through the boiler before reaching the filter. If a boiler is installed on the lower levels of a of the heating system (dense debris tends to settle on the lowest levels the most), it is likely to be affected even more. System and combination boilers have internal pumps, and the combination boiler often has a diverter valve,  which all are affected by magnetic debris being present. If a magnetic filter where installed after the pump and the motorised valve(s) on a conventional system, as per the diagram, any contaminated water will pass through the magnetic fields of the pump and the valves before they pass the magnetic filter. In our experience, most filters are installed in position B or in other locations within the central heating system that are not effective. By installing the filter at any point in the system other than position “A” you drastically reduce the effect of the filter.

There is only one piece of equipment that can effectively remove up to around 95% of the debris found within a central heating system, that is a power flush machine. When a heating system has been power flushed, is correctly treated with inhibitors and the adequate levels of inhibitors are maintained over the systems lifetime, the rate of corrosion occurring within the heating system will be reduced drastically. A central heating system can go for many years with no ill effect from debris once it has been power flushed and treated with inhibitors correctly. Not only does power flushing remove corrosion from the radiators and inhibitors slow the corrosion process, but both will also prevent scale and microbial growth from ever being a problem when the right chemicals and processes are used.

To give you an example, FORTHRIGHT was instructed to change a 3-port valve passing in Cheltenham in summer 2014. The customer was advised to power flush the system as the previous valve had failed as a result of sludge. The customer ignored the advice we gave and within ten months the newly installed valve had failed.

Magnetic filtration can compliment a correctly power flushed system when they are installed in the correct position (in position “A”), however as the debris produced from a system following a power flush and treatment should be minimal, you need to consider the cost to benefit ratio when installing a filter. There are several market-leading companies, as well as many local companies, that are charging more than £300.00 to fit a magnetic filtration device! Considering that FORTHRIGHT will power flush and treat a central heating system correctly with prices starting a little more than this, and the fact that magnetic filtration can only collect some of the material that passes through it, we would advise homeowners to save the money for the next flush in 20-30 years time. 


Companies like FORTHRIGHT are far and few between. If you are local to us and need a power flush in Cheltenham, Gloucester, Tewkesbury or the surrounding areas, then you would be wise to contact us. Unlike other companies, we do not charge a single penny in labour to fit a filter, just the cost of it, of which we will always advise the Fernox Omega filter. 

FORTHRIGHT are not criticising magnetic filtration products or the manufactures; we are however against the miss-selling of these products and the marketing that can take place to promote their use. Once any system is power flushed and treated correctly non-magnetic filtration will not be required as it will have removed such debris from the system.

Magnetic filtration can be a benefit; however, it is important to remember that it is merely an additional product that will provide ‘some’ extra protection to some parts of your heating system. The cost of installing this equipment needs to be practical for it to be a benefit, as in a heating system that is power flushed and treated correctly, any corrosion will be minimal. It will take a very long time for corrosion levels to accumulate to a point where they could cause a problem and have a noticeable adverse effect on efficiency so long as inhibitor levels are maintained. By installing a magnetic filter in the correct position, it would likely increase the time it would take for corrosion to hurt the central heating system and its components, but is the cost worth it? 

To learn more about power flushing click  here.

If you are looking for a professional company to correctly undertake a power flush in Cheltenham, Gloucester, Stroud, Tewkesbury or any of the surrounding areas, contact FORTHRIGHT! We will not sell you anything that does not benefit you or your home!