Why aren't central heating biocides widely available?

D

DIY10291

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Last autumn, I cleaned out the central heating system (old back boiler with F&E) with X400, and dosed with X100. It hadn't been touched for a good few years prior to that. A few months later, I find this gunge in the tank (stringy/white stuff) which Google tells me is probably bacterial and caused by the inhibitor. I baled out most of it but it came back quickly.

I am not sure what to do now. It looks like a good option would be to bale out the tank, hoover it dry, wipe with bleach and add some kind of biocide. But I can only see a few biocides in SF/Wickes/Toolstation, and they're all made for underfloor systems. What should I do, and why are biocides for my problem unavailable in the big plumbers merchants (which makes me think either my problem is rare or the chemicals don't work for it)?
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I'm certain it's because most people don't ever buy one so the DIY retailers don't bother to stock it. you may need to order even from a plumbers merchant.

if your system seems to be infected, you need to bale out and scrub clean the F&E tank first, including the lid, valve and float, and then give the system a chemical clean and rinse. Then you will have reduced the load of spores and bacteria, and hopefully flushed away any organic material it can feed on. Ensure it is not pumping over. If there is a leak, fresh water will top it up and dilute or wash away the biocide.

does the F&E have a tight-fitting lid, and is it free of dust, dirt and drowned wildlife?

Once it is clean, you can wipe round the F&E with your biocide and add the approved amount. It is normal to have a higher concentration in the F&E than in the pipework, which is inhospitable to life, so add about half during filling, with the inhibitor, and about half when filled.

wiping with bleach will temporarily reduce infection, but the bleach washes away, and degrades into salt and water. Salt encourages corrosion.
 
p.s.

add an insulating jacket, which will help protect it from getting warm on sunny summer days.
 
I use Fernox AF10, but I believe there are others. You can order it from a plumbers merchant if not on the shelf
 
It's normally multiple people putting in different inhibitors. Add some gunge and bacteria and then 50 degree summer heat. And normally Trvs and no bypass and you get hot circulation around the header tank.
 
JohnD said:
I'm certain it's because most people don't ever buy one so the DIY retailers don't bother to stock it. you may need to order even from a plumbers merchant.

if your system seems to be infected, you need to bale out and scrub clean the F&E tank first, including the lid, valve and float, and then give the system a chemical clean and rinse. Then you will have reduced the load of spores and bacteria, and hopefully flushed away any organic material it can feed on. Ensure it is not pumping over. If there is a leak, fresh water will top it up and dilute or wash away the biocide.

does the F&E have a tight-fitting lid, and is it free of dust, dirt and drowned wildlife?

Once it is clean, you can wipe round the F&E with your biocide and add the approved amount. It is normal to have a higher concentration in the F&E than in the pipework, which is inhospitable to life, so add about half during filling, with the inhibitor, and about half when filled.

wiping with bleach will temporarily reduce infection, but the bleach washes away, and degrades into salt and water. Salt encourages corrosion.
Click to expand...
Having forgot about this for a month, I contacted Sentinel, if anyone is interested:

"We are inclined to think (and it certainly looks like that on the images) that this is a case of bacterial/microbiological contaminant build up. After cleaning the header tank well, you can use our X700 Biocide as it is specifically developed for low temp (<60C) applications and can be used in the header tank. If the X700 remains in the header tank it would be fine but you do need to keep your eye on it as the liquid in this tank mixes and circulates through the heating system so you may need to top it up. Our X100 and X700 are perfectly compatible and combined would not cause any issues."
 
Just had a thought - could I clean out the tank, then leave the tank empty (or even drain the whole system) until winter? Could I kill off the infestation this way, by starving it of water?
 
No

I don't know about central heating bacteria, but excavating builders rummaging through plague pits in London got bubonic plague after three hundred years.
 
Don't worry, it's a temporary matter, it'll become available everywhere soon with the current trend toward low temperature operation of heating systems and the revisions to Part l of the Building Regulations stipulating 55degree flow temps on new installs.
 
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