Alternative to Fernox AF10 biocide

[Cynic]

As a boy we used vast quantities of 40% formaldehyde around the market garden. Very few organisms could survive that.

[Paul]

replying to Aidan, Paul wrote: I had this problem 3 years ago. I contacted Fernox who recommended AF10 but said there are two types of bio infection you can get in a heating system. They can test your water - at a cost! But suggested I try AF 10 first. I managed to get some off eBay at the time and after flushing my system and scrubbing the header tank, I added fresh inhibitor and AF10, several weeks later there were signs of return, so I immediately bought another biocide -this time managed to buy it locally at an Indy plumbers merchant, sorry can?t recall the name of it, added this to the header tank and it all went away! Moral,of the tale - buy twice as much as it says on the bottle! Three years on, it has not returned. Where did it come from? Well, the roof space is an eco system of its own and I guess we?ll never be sure, but make certain your header tank is well insulated and - just as important- sealed as much as it can be so that nothing can get in it and / or contaminate it such as insects, my theory being you can only get a ?bio? infestation from an organic origin.