Floating mat of scum on FE tank

[chudsy]

Hi All,
Just about to drain the sytem down and when I went to tie up the ball valve there was a layer of slimey light brown stuff floating on the top of the tank which was like the skin on rice pudding!
I picked most of it up and made sure there was nothing down by the outlet.
I mopped out the tank on the last drain down when I put boiler silencer in. Could this be the left overs of the clean?
I'm about to treat it with X800 as advised by one of the chaps on here as it kettles like hell then shuts down so hopefully this will clear any blocks and debris.
Pump was changed a few months ago to a 15/60 & boiler is Ideal RS80N.
Regards
Paul.

 

[ollski]

Its a bacterial film from the chemicals in the system not dragged through properly usually.

 

[JohnD]

Bale out all this stuff, sponge out the F&E, scrub it clean, and and swab it (and the lid) with bleach to kill the stuff. You can buy an expensive chemical by Fernox called "AF-10 Universal Biocide" that will prevent a recurrence for a year or two. You can also add a couple of teaspoonfuls of bleach into the F&E after you have finished filling the system and it has settled down, but it will gradually be diluted by water movement.

Apart from the brown mat, you may get transparent bacterial slime, which is quite disgusting, but the same bleach and AF-10 will kill it.

Modern anti-corrosion chemicals, which I expect you will be adding, may do some good.

A tight-fitting plastic lid, and an insulating jacket, will keep out organic material such as dust, dirt and spiders, and will stop it getting so warm in summer.