Best Magnetic Filters Re January 29, 2021

Best Magnetic Filters

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Have you ever wondered why your radiators are making a strange noise, or why they only warm up at the top but not the bottom?

It is most likely a result of what professionals call ‘sludge’ build-up. ‘Sludge’ is a common industry term for a build-up of rust and debris in the system, which builds up in open-vented systems. ‘Grit’ is another term professionals use to describe a harder form of debris that occurs in sealed systems. 

The dirt and debris known as ‘sludge’ can result in cold spots at the bottom of your radiator, this is because the rust settles at the bottom in piles. This effectively makes your heating system less efficient, will cost you more in energy, and could also result in the need for an expensive system cleanse. 

How can you prevent this from happening you ask? Well, a magnetic filter could be the answer!

If you are interested in a guide on other ways to increase your boiler lifespan, we have this covered in our 7 ways to increase boiler lifespan blog.

What is a magnetic filter?

A magnetic boiler filter is a metal or plastic component which is connected to the return pipework on your central heating system. It is located as close to the boiler as possible. This is to catch the ‘sludge’ before it has the chance to enter your boiler. 

It has a powerful magnet that grabs the dirt and debris also called ‘sludge’, that builds up in the system over time and filters it out. Yes, it’s that simple. 

A magnetic filter is cleaned by a Gas Safe engineer during your annual boiler service. 

To have a magnetic boiler filter supplied and installed by your heating engineer usually costs around £150-£275. However, we will go more into depth about cost later on in this blog. When our customers ask ‘Do I need a magnetic filter for my boiler?’ or ‘Are magnetic filters worth the cost?’, we always give the same answer, a resounding yes! They are basically a filter to stop any nasty stuff from getting into your precious boiler. Every boiler sold by WarmZilla comes with a free system filter, that’s how important they are in looking after your boiler.


What are the most popular magnetic filters?

There are numerous magnetic filters to choose from when purchasing a new or replacement boiler. 

This section will aim to discuss the most popular magnetic filters and describe why, so you can choose the best one for your boiler.

Adey Magnaclean Atom

  • Protects against damaging effects of black iron oxide sludge
  • Compact design
  • Can fit on your existing central heating system 
  • Supplied fully assembled and ready for installation, saving time-on-site
  • 2-way valve has a white indicator to show what mode the filter is in
  • Only 115mm needed to install so can fit into even the tightest of spaces

Adey Pro 2

  • In-line installation can be completed in just two minutes
  • 360° rotational valves for multiple installation options
  • Bi-directional flow means either port can be an inlet, increasing flexibility
  • Ultra-thin sheath to enhance magnetic capture
  • Low profile drain valve designed for easier servicing and dosing
  • High capacity
  • Compact design
  • Easy to install – fits on horizontal and vertical pipework in both flow directions. The filter can operate at an angle of 45°
  • Unique action
  • Removes magnetic and non-magnetic contaminants from system water
  • Unique manifold with double radial seals and multiple orientation capabilities

Sentinal Vortex 300


  • Dual seals with no requirement to replace at annual service
  • Manufactured to automotive standard TS16949 using high-quality brass valves
  • Two size options: large and compact
  • Anti-tamper drain valve
  • 360° positionable T-piece
  • Powerful 9000 Gauss magnet assembly with innovative Vortex Core

Spirotech Spirotrap


  • Dirt can be drained while the system is in operation
  • No shut-off valves or bypass required
  • Constant low-pressure drop
  • Maintenance only takes a few seconds and is not a dirty job compared to a filter solution
  • No unnecessary downtime

System Filter Brand Comparison Table

MakeAdeyAdeyFernoxSentinal SpirotechAltecnicGrant
Pro 2TF1 OmegaVortex 300SpirotrapDirtmag IQVortex
TechnologyStandard filterStandard filterStandard filterVortex (Screw) – slows down water to improve retentionCyclone – ‘spins down’ particles to the bottom of the collection chamberWater hits internal mesh and drops to bottom or attracts to magnetic if rustStandard filter
Warranty10 years10 year25 years10 years20 years1 year2 years


Do I need a magnetic filter?

Magnetic pumps are not essential, however, they are highly recommended. 

Here at WarmZilla, a Worcester Bosch System Filter will be supplied and installed for free when purchasing a Worcester Bosch boiler. 

We offer either the Mini Worcester Bosch Greenstar System Filter or the Maxi Worcester Bosch Greenstar Filter. Both have great features including :

  • Magnetic and non-magnetic filtration to collect a wide range of system debris
  • Isolation valve indicators to visually assist when isolating the filter
  • Drainage point at the bottom for ease of access during servicing
  • Can be installed both under and over the boiler or remotely
  • Detachable body for ease of service and power flushing
  • One-way valve for ease of adding system chemicals

Depending on your boiler and central heating system, we will install either:

The Mini Worcester Bosch Greenstar System Filter


Length (mm)230
Height (mm)145
Width (mm)210
Weight (kg)2.2
Effective volume of magnetic length21,974 mm3

Canister size (with valves in closed position)


Or the

Maxi Worcester Bosch Greenstar System Filter

Length (mm)230
Height (mm)209
Width (mm)180
Weight (kg)2.02
Effective volume of magnetic length36,500 mm3

Canister size (with valves in closed position)


Magnetic system filter installation costs

Your Gas Safe heating engineer will be able to install your boiler’s magnetic filter however there are a few checks they will need to do beforehand. The first is to check the size of the pipes that run to your boiler. Magnetic filters often come in different mm sizes to accommodate the size of the pipes. It is important to remember that this could have an effect on the price of your filter. 

As you can see above, the price of your boiler magnetic filter can vary depending on the supplier. The prices in the table above are based on a 22mm pipe. The price of a 28mm magnetic filter may be between 34-40% more than this. 

Once you’ve decided on a filter (costing between £60-150), the next cost is the actual installation cost.

On average, it costs around £100-£150 for the installation of your boiler magnetic filter. Unless of course, you purchase a Worcester Bosch boiler with us, you not only get a Worcester Bosch Greenstar System Filter, but the installation cost is already included in the price package. What more could you ask for!

In total, boiler magnetic filter supply and installation normally cost around £150- £275 approx.

Installation of a boiler magnetic filter can take anything from 1 to 4 hours to fit. This will depend on the ease of access to the filter and if any adjustments to pipework need to be made.

We know that these extra costs seem like a lot right now, but you will see the benefits from the money savings you will see on your heating bills and also any future maintenance if necessary.

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

Power flushing


As a result of not having a magnetic filter installed, over time your system will collect a build-up of debris and rust. Very often, when this happens, for the best system cleanse results, a powerflush is suggested. 

A powerflush is when chemicals are passed through the system at a very high pressure to remove all the contaminants. Whilst flushing, all radiators are turned off and one opened at a time in order to focus that machine on that section. Each radiator is turned on one at a time until all the radiators are done. 

Although this results in a thoroughly clean heating system, a powerflush can be very damaging to your pipes. The power can be too vigorous and shake the pipework, resulting in leaks. For this reason, we at WarmZilla do not offer a powerflush, and recommend that you look into a magnetic filter to prevent this from happening. 

For more information on powerflushes, have a read of our ‘Differences of a Powerflush, Chemical & System Flush?’ blog.

Approx costs for a powerflush:

  • £500-£600 incl VAT 6-10 radiators
  • £600-£750 incl VAT 11-15 radiators

Radiator flush with a chemical cleanse

A radiator flush and chemical cleanse is a strong chemical that is added to the system and left for a period of hours or days (depending on the strength of chemical). This chemical then works its way through the system, breaking down the rust and debris. This is then drained down, the radiators are flushed and then filled back up with clean water. The majority of the time, this is where the inhibitor is added. 

Approx cost:

  • £380 incl VAT 6-10 radiators
  • £420 incl VAT 11-15 radiators

VDI 2035 demineralising methods

An alternative to chemical treatments is a process know called VDI 2035.

This process naturally treats the water to prevent corrosion. A device called a deaerator to remove air from the system on an on-going basis is used. It is important to note that not all boiler manufacturers will accept VDI 2035. It is likely that if your installer uses this method then he or she fits boilers that do accept it.

Approx cost:

  • £150 incl VAT per hour
  • Cost of the filter varies according to the product

Can I add a magnetic filter to my existing heating system?

If your thinking about buying a new or replacement boiler, it may be worth noting that some boiler manufactures have their own magnetic filter.

It is important to note that if you are attaching a magnetic filter to your existing central heating system, your heating engineer may suggest a system cleanse to extract any built-up debris and rust before fitting the new magnetic filter. This could be costly, so speak with your engineer first.

When buying a new boiler from WarmZilla, a system flush will be included in your price package, for extra peace of mind. 

If you are interested in purchasing a new or replacement boiler, click here for a quote in minutes!

If you choose to have a magnetic filter, this is usually fitted during initial installation when getting a new or replacement boiler, however, the answer is yes, you can add a magnetic filter to your existing heating system. This should be installed by a Gas Safe heating engineer. 

It is also important to check with your heating engineer that having a magnetic filter is practical for your boiler due to its location. 

Do I need to clean my magnetic filter?

You will need to get the ‘sludge’ that is magnetically cleared by your filter removed every now and again. However, this is normally done by your Gas Safe heating engineer during your annual service. 

Overall, in order to prevent your central heating system from becoming less efficient from a build-up of dirt, debris, and rust, we recommend a boiler magnetic filter. 

There are different ranges of magnetic filters, some more cost-effective than others, however, a magnetic filter will save you a lot of money in the long run. 

We hope that this article has given you some insight into the different magnetic filters on the market and helped you decide which one is best for you and your new or replacement boiler.

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