Fernox TF1 Omega magnetic filter

[Avocet]

Hi All,

I have a Fernox TF1 Omega magnetic filter in our central heating system. The instructions say to take the magnet out and open the taps "until the water runs clear". I've done that and after three, 1 litre jugs full, the water is still absolutely black! When I emptied the first jug, there were a few "hard bits" of black (magnetite, I'm guessing?) in the bottom. Fewer in the second and none in the third jug. However, the water itself, is still black. Is that normal?

Also, I've obviously brought the system back up t pressure (it's a combi boiler with an expansion vessel) by adding more water from the fill valve. Do I need to dose the system with more inhibitor now, please?

 

[Madrab]

Nope, not normal - if you are talking about the drain tap in the bottom of the filter body then it would only run clear after say the volume of what's in the filter once the magnet is flushed clean and if the CH system water was clean & clear.

Afraid to say if it's still running black after 3 x1Ltr jugs of system water, then your CH system looks like it's badly needing cleaned and flushed.

 

[Avocet]

Nope, not normal - if you are talking about the drain tap in the bottom of the filter body then it would only run clear after say the volume of what's in the filter once the magnet is flushed clean and if the CH system water was clean & clear.

Afraid to say if it's still running black after 3 x1Ltr jugs of system water, then your CH system looks like it's badly needing cleaned and flushed.

OK, thanks. No, the stuff that came out of the filter housing itself was maybe "a bit" thicker and blacker than subsequent jugfulls but they were all pretty black. A typical translucent, plastic, 1 litre kitchen measuring jug. If I chucked a 5p coin into it, I wouldn't be able to see it at the bttom of the jug, even after 3 litres!

Supplementary question: How often would you expect to empty a filter like that? I've been doing it once a year. Should it be more often?

 

[endecotp]

I've been doing it once a year.

So is the blackness new since last time you emptied the filter?

What’s the history?

 

[Avocet]

So is the blackness new since last time you emptied the filter?

What’s the history?

1995 system. Worcester Heatslave combi oil boiler. A dozen or so steel radiators. House seems to have been built with a mixture of micropbore copper and plastic pipes. The house was 5 years old when we moved in. Two of the radiators in bedrooms that we didn't use much, (and therefore had the radiators turned down a lot of the time) went cold. (They were also the two furthest from the boiler). The plastic pipes were jammed full of some sort of black crystals. This would have been about 10 years ago and when I drained the system at the time, what came out was very black.

I managed to replace both pipes without pulling the floors up, and I think the problem might have been that they were single-skinned plastic pipes? The stuff I used to replace them was double-skinned. I still have one radiator that's cold (which I can't easily get to the pipes for, but it's only small and we never used it anyway. I bet it's also the single-skinned plastic pipe. The two in the bedrooms where I replaced the pipes, have been fine since.

I've tried various system cleaners over the years, - Fernox, Sentinel, etc. None have made any difference. I've always added inhibitor when re-filling the system. It has probably been drained four or five times in the 25 years we've lived here - once to replace those pipes, once to replace the expansion vessel on the boiler, once to fit some TRVs, once (October 2022 to fit this filter, and the most recent being when the pump failed (original, as far as I could tell). That was only about 18 months ago, so the water in there is about 18 months old.

 

[Madrab]

Supplementary question: How often would you expect to empty a filter like that? I've been doing it once a year. Should it be more often?

A well condition system wouldn't need it's filter checked/cleared more than annually. If the system is black then the filter (magnet) will be working to ensure no debris gets past it and into the small waterways in the main HEX and plate, that's primarily why they are installed in the UK.

The key is a nice healthy system that stays clean throughout it's lifetime, minimising the formation of magnetite. If you are handy then a clean and gravity/mains flush should be relatively straightforward to perform, then inhibit the system properly after that and monitor.