Filters on a central heating system

  al's left peg 16:45 26 Sep 2012

Hi guys,

Anyone on here have any knowledge / experience of these filters fitted on the return pipe to a boiler?

The common ones are 1) Maganclean, 2) Fernox TF1 and 3) Spirotech Magnabooster.

I have a 10 year old Vokera boiler which is probably in need of replacing, but I have been looking at the items above as a way to arrest sludge build up in the pipe system. They also incorporate magnets to trap any metal fragments which can damage the boiler.

When my central heating is running it makes a bit of noise in the pipe work, and I have been told this is due to sludge in the pipe work. I can testify to this when I remove a radiator and flush it in the back garden with a hose pipe, it runs black for 5 minutes before the water turns clear.

If anybody has any knowledge regarding these filters can you post your views to me on here? I have been looking at a few DIY forums, and for everyone professing how good they are, there is another saying they are not worth the money. I expect at least one reply from the F.E as he seems pretty schooled up in these matters. Regards, Al

  Forum Editor 17:05 26 Sep 2012

The really effective way to remove sludge from a central heating system is to have it power flushed by a heating engineer. This involves connecting a special flushing machine into the primary circuit and pumping a flushing solution through the system for an hour or so.

At the end of the process you'll have a spotlessly clean pipe circuit and a reasonably big hole in your wallet (£150 to £250).

An alternative method is to buy a flushing agent - cost about £40 and add it to the system - you can get one that you squirt in via the air-bleed valve of a radiator.

Once the flushing liquid is in, run the heating system on a high thermostat setting for 4 or five hours non-stop. Turn everything off, drain the system, refill with clean water and drain again. you'll be amazed at the amount if filth that comes out when you drain down.

Now add a corrosion inhibitor (same way as for the flushing agent) and fill the system.

It will run much more smoothly, and the pipes will stay cleaner. The corrosion inhibitor will see to that. Ideally you should repeat the process every 18 months or so.

  wiz-king 17:58 26 Sep 2012

I have a centrifugal filter fitted and the amount of muck it took out was amazing, I had to empty it everyday for the first few weeks then monthly.

  lotvic 00:13 27 Sep 2012

Engineer fitted a Magnaclean filter on my 30 year old system when I had boiler replaced. System was flushed first as part of the overhaul. Engineer was full of praise for them, said it made their job easier as they could tell from contents of filter cache the state of circulating water etc.

  natdoor 08:46 27 Sep 2012

If you have a reasonably large system, ten radiators or more, then in my experience the cost will be at least three times FE's suggestion. I base this on estimates from BG and several independent operators. Of course, if FE has access to a good, cheap tradesman, then I'm sure that we would all like his details.

Magnaclean will help but is no guarantee that sludge will not accumulate in the system, such as in an air separator, if fitted. Note that removing radiators to flush them is fine but make sure that inhibitor is used when refilling, otherwise you are only storing up trouble.

  onthelimit1 09:10 27 Sep 2012

My 17 yr old ststem started making banging noises from the boiler. i drained down the system (including the drain on the boiler itself). Refilled with the cleaning agent already mentione, and bled the radiators. Ran it for a couple of days, then drained down as before and refilled with inhibitor. Bit of work to do, but for a cost of around 30 quid, I now have a quiet system again.

  amonra 15:50 27 Sep 2012

Corrosion is part and parcel of any normal C/H system. You have a mixture of copper, brass and iron which all react with each other in the presence of hot water. The common anti-corrosion agent Fernox is quite effective for a while but needs to be renewed every so often depending on the size of the system and the acidity/alkalinity of the water. So sludge is inevitable and unless it builds up to a level that interferes with the normal flow of water, it is best left alone. Normally, the chemical reactions between the differing metals which produces the sludge reduces after a while as the reactions die down, so no more sludge is produced. Power flushing etc. only exposes new metal surfaces which starts the process all over again. If your system has air-leaks, this can aggravate the process by introducing fresh oxygen into the system thereby causing more metal corrosion and more sludge. It's a never ending cycle. Good luck with any filters you fit, just remember that they will need cleaning every so often, which means fresh oxygenated water introduced, which means more corrosion, which means...............

  Forum Editor 16:10 27 Sep 2012


"So sludge is inevitable and unless it builds up to a level that interferes with the normal flow of water, it is best left alone."

If you use a corrosion inhibitor, and renew it at the correct intervals sludge is not inevitable - your system can remain sludge-free.

If you don't do that you will get sludge in the system, and it will impede the flow of water as it builds up - that is certainly inevitable. The sludge will tend to collect in the bottom of radiators that are furthest away from the circulating pump. The effect is cumulative - as sludge accumulates the flow rate is impeded, and the radiator can become a 'dead leg' on the system, with little or no flow at all.

The only real way to clean a system totally is to power flush and add inhibitor.

As for air leaks - if a central heating system has an air leak it will also have a water leak, so it is likely to be fixed pretty quickly - oxygen being introduced via air leaks isn't of any significance at all.

  al's left peg 20:18 27 Sep 2012

Thanks for the comments so far. I still am unsure as to wether A filter would be worth installing in my system. I have heard the Magnaclean can leak as it's construction is plastic.

The TF1 is manufactured by Fernox who also manufacture the inhibitor and cleansers mentioned on here.

The Spirotech is a brass construction so would be the strongest of the lot. I am considering installing a drain off point in my system which will flush the whole system down to an existing outside drain, but it would mean lifting my living room floor to do the job.

  onthelimit1 08:50 28 Sep 2012

There are usually drain points on one or more of the downstairs radiators. A length of hose and a jubilee clip is all that's needed. However, as I mentioned before, you do need to do the same to the boiler as the tank it feeds is normally on the first floor and water will be left in the boiler circuit after the rads are drained.

  Diemmess 12:47 28 Sep 2012

Have just had a long conversation with a very good local plumber. On the principle that "if it isn't broke don't fix it" their advice is don't power flush a system unless it involves a new boiler. The manufacturers insist this is done or the warranty is void.

With an older system the very real disturbance will almost certainly soon show as pinholes in radiators.

Corrosion inhibitors are fine to delay or stop corrosion, but do nothing to cleanse, also piecemeal flushing of a particular radiator if necessary. If the system is so clagged up that some flushing has to be done, then bite the bullet and hope you haven't left it too long.

I asked the plumber because I have a gravity fed anthracite boiler which I would be reluctant to replace. No gas in this village and oil would not give the gentle background warmth my old Trianco gives day in day out.

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