The Ultimate Guide To Boiler Magnetic System Filters [And Why You Need One]

By | 17th March 2017

Over the last decade or so, power flushing has become less and less popular. This is partly since magnetic system filters (or sludge filter) for boilers are becoming more popular.

Power flushing gets rid of debris that has collected in a system. And up until recently it used to be the best solution.

However, magnetic system filters catch most debris and it’s a great idea to have one fitted. Using one means that a power flush doesn’t have the impact that it used to.

Not sure how much a magnetic system filter costs? Check out boiler filter prices here.

And, if you want someone to help fit the boiler filter, Click Here

If you have any further questions or need a magnetic system filter installed, please leave a comment at the end of the article.

What is A Magnetic System Filter, and How Does it Work?
Do You Need a Magnetic System Filter?
Why a Sludge Filter is NOT an Alternative to Inhibitor
What Happens If a Magnetic Filter is Not Fitted
Magnetic System Filter Installation Costs
How to Maintain a Magnetic System Filter
Best Magnetic System Filters

What is A Magnetic System Filter, and How Does it Work?

A heating system is built using various metal components. Take your radiators and copper piping for instance. As the years go by the insides of the pipe and radiators rust. This rust breaks off and starts to circulate through the heating system.

This is combined with dirt and scale that is contained in the water in your system. Together, these particles form central heating sludge.

This is where big problems start to occur. The sludge settles in places that cause major issues. A typical example is at the radiators.

Have you ever wondered why radiators are warm at the top, but not at the bottom?

Have you had a recent pump failure on your boiler, or had to replace the heat exchanger?

Expensive repairs, right?

These are common symptoms of sludge build up. And, a magnetic system filter is designed to catch this sludge.

Check out this video from MagnaClean. You can see how the magnetic system filter tackles sludge in a matter of minutes.

As you can see, the sludge circulates around the heating system. The magnetic system filter catches most this sludge as it passes through the filter. The filter can then be emptied to ensure it doesn’t fill up (and stop protecting your heating system).

Do You Need a Magnetic System Filter?

We regularly get asked if a magnetic system filter is a necessary addition to a heating system. The answer is always yes.

We never replace a boiler without fitting a sludge filter alongside it. And here is why.

Boiler manufacturers warranties. A lot of top boiler brands will insist two things for their warranty to be valid.

  1. The heating system should be correctly dosed with inhibitor. This helps break the sludge in the system down.
  2. The heating system should have a sludge filter installed. This ensures that any faulty components are faulty, and not just the victim of sludge.

So, it’s worth checking manufacturer terms and conditions to ensure that you warranty is valid if you don’t currently have a magnet filter installed.

Many people ask us why there isn’t a magnetic system filter already installed if they are so important. Well, one of the top brands is Adey (they produce MagnaClean filters). The brand was created by Chris Adey back in 2003 and the filters started coming to market.

It took a good few years for them to become popular so most boiler installations before 2008 won’t have one installed. The only exceptions seem to be heating specialists that suggest a homeowner have one installed to protect their heating system.

Why a Sludge Filter is NOT an Alternative to Inhibitor

Inhibitor will work in tandem to a system filter. The inhibitor works hard to break down any debris in the system. Without inhibitor, a lot of the stubborn debris build up will not be broken down. Instead it will settle in places such as the heat exchanger and radiators.

When inhibitor is correctly dosed in the system, it will allow broken down debris to flow in the heating water. This makes its way back to the return where the sludge filter is waiting to collect it.

What Happens If a Magnetic Filter is Not Fitted

Sludge is an absolute killer when it comes to central heating systems. It doesn’t just affect one part of the heating system, but all of it. If you have sludge present, or it’s building up, you’ll experience things like:

  1. Radiators are hot at the top but they won’t heat up at the bottom.
  2. They don’t get hot at the top until you bleed them, and you must bleed them regularly.
  3. The boiler is making strange noises such as banging or gurgling.
  4. Some radiators don’t get up to the temperature you require, even when the stat is set to maximum.
  5. The boiler pump has started leaking, or you’ve had multiple pump failures.
  6. Pipes to a radiator get hot, but the radiator never seems to heat up.
  7. When broken parts from the boiler are removed, they are full of dirt.
  8. The return on the boiler is cold (or Luke-warm), even though the flow is boiling hot.

Problems from sludge build up quickly compound. Sometimes they get so bad that aspects of the heating system need to be replaced (such as radiators, the boiler pump, or rad valves).

The magnet filter will not act as a total cure, as it’s more of a prevention method.

Magnetic System Filter Installation Costs

Any heating engineer will be able to install a boiler system filter.

The first thing they will do is check to see the size of the pipes that run to your boiler. This makes a difference to the price of a filter. Some lesser known brands might charge £50-60 for a 22mm sludge filter. However, a 28mm version of the same filter is likely to cost 35-40% more than this.

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

Expect to pay £100-150 for the installation. In total, the magnetic system filter installation will be £150-275. This is certainly a ballpark estimate for installation costs. A sludge magnet 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.

One other consideration when having a boiler filter fitted, is it’s worthwhile having a flush. Even a quick manual flush of the heating system is a good idea.

This will get rid of most the debris in the system, so the filter doesn’t get blocked. Another option is to have the heating engineer come back a week later and clean out the filter. The filter will have caught most sludge in the system so will be good for another 12 months without any maintenance.

This cost is easily offset by the money savings you’ll see on heating repairs over the years, not to mention that the filter will help to keep your central heating running much more efficiently.

How to Maintain a Magnetic System Filter

Like all parts of your central heating system, a magnetic boiler filter will need to be maintained on a regularly basis. We always suggest that the filter should be checked and cleaned every 12 months.

Luckily, this coincides with most boiler schedules. If you don’t have an annual boiler service already, I’d certainly suggest you book one in. When the Gas Safe engineer arrives, ask them if they can inspect and the clean the filter out.

If the filter is easy to access, this shouldn’t add much to the cost of your service, as it only takes 15-30 minutes to clean out. A quick inspection and clean is all the maintenance that a filter will need.

You can learn more about boiler servicing costs here.

Best Magnetic System Filters

It must be said that MagnaClean magnetic filters seem to be the brand of choice for both plumbing merchants and most heating engineers.

The Prices we’ve listed below are for 22mm system filters, as these are the most common.

Some pipe work to some boilers will be 28mm and 28mm filters are slightly more expensive. If you have 28mm pipe work, expect to pay a little more for your filter.

The filters can be purchased from all reputable heating and plumbing merchants across the UK.

Fernox TF1

Fernox is one of the most reputable brands in the filter industry. The Fernox TF1 offers excellent value for money from a brand with this much weight. Here’s out guide to the Fernox TF1.

Buy on Amazon.

Worcester Bosch’s System Filter

Generally, we stick to Instinct, Fernox and MaganClean filters. However, if you are planning to have a Worcester Bosch boiler installed, then get their own brand filter. By using their filter, you will get an extra years warranty on your boiler.

However, bear in mind Worcester Bosch magnet filters are one of the most expensive on the market.

Buy on Amazon.

Instinct Eco-Mag

The Instinct Eco-Mag filter comes with a 2-year warranty and is an excellent budget filter that has become increasingly popular over the last few years.

The MagnaClean range (Micro and Professional) from Adey

Price: prices start from £70 for the MagnaClean Micro, and £85 for the MaganaClean Professional 2 Chemical Pack. We’ve created a full guide to MagnaClean filters here.

Buy on Amazon.

Adey are probably the biggest supplier of magnetic system filters in the UK. Even so, their prices are incredibly reasonable.

The MagnaClean Micro is the smaller filter on offer. If your budget allows, then it’s certainly worth going for something bigger such as the MagnaClean Professional Chemical Pack.

What’s Next?

If you have any questions regarding magnetic system filters, please leave a comment below and we’ll get back to you as soon as we can.

And, if you need a quote for boiler filter installation, click here.


2 thoughts on “The Ultimate Guide To Boiler Magnetic System Filters [And Why You Need One]

    1. heatingforce Post author

      Hi Marc,

      The return pipe.

      That gives the flow water the chance to break everything up ready to be caught by the filter, just before it reaches the boiler.

      Fitting it on the flow means any debris would have to pass through (or get stuck in) the boiler before reaching the filter.

      Hope that helps 🙂


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