Fungus/growth floating on top of feed & expansion tank?

[Koko88]

I’ve recently cleaned my central heating system with Sentinel X400 cleaner, flushed it out clear, refilled & added Sentinel X100 inhibitor.

After a couple of months, I went to the loft to check the feed & expansion tank, open the lid, there’s some kind of white/yellowish fungus/growth floating on top of the water?

How to get rid of it without having to completely drain the system out, flush it out again?

Is there any stuff you can buy to add into the system to get rid of it?

 

[Chuck]

One of the side-effects of running CH systems at low flow temperatures (to promote efficiency) is that biofilms form in the header tank.

To avoid drawing muck down into the system, I would plug the outlet then empty the tank with a pump or siphon and use some diluted bleach to clean. The biofilm etc. is potentially hazardous to health so use gloves, googles and mask.

Whether it's necessary to drain the whole system is debatable. I probably wouldn't bother if this is a first attempt to deal with the problem.

I use Fernox F7 for prevention. Sentinel will have something equivalent if you want to stick to one brand, which is probably a good idea. Depending on the age of the system and boiler, I'd also consider sealing the system and getting rid of the F/E tank.

 

[fowlerboi]

How did you add the cleaner to the system?

 

[Koko88]

How did you add the cleaner to the system?

Through the outlet in the feed & expansion tank

 

[fowlerboi]

While the system was empty and then re-filled?

 

[Koko88]

While the system was empty and then re-filled?

Yes

 

[Koko88]

One of the side-effects of running CH systems at low flow temperatures (to promote efficiency) is that biofilms form in the header tank.

To avoid drawing muck down into the system, I would plug the outlet then empty the tank with a pump or siphon and use some diluted bleach to clean. The biofilm etc. is potentially hazardous to health so use gloves, googles and mask.

Whether it's necessary to drain the whole system is debatable. I probably wouldn't bother if this is a first attempt to deal with the problem.

I use Fernox F7 for prevention. Sentinel will have something equivalent if you want to stick to one brand, which is probably a good idea. Depending on the age of the system and boiler, I'd also consider sealing the system and getting rid of the F/E tank.

Sentinel X700 biocide is very expensive, I’m considering using Everbuild P26 biocide as it’s more affordable?

I presume using a different brand of central heating system biocide should be ok, better than nothing?