My 12 year old CH boiler (old style header tank-in-loft type) is getting noisier and noisier, it sounds like someone is inside trying to beat their way out - bang, clunk, bang! not really noticed it too much before but since having to turn up the heating a bit and run it longer through the night these last few weeks it is getting on my wick!
I am told it's probably 'Kettling' and as I live in a hard water area, it is probably due to a thick layer of lime scale in the boiler.
What is also interesting (or maybe not) I flushed & drained the system a couple of months ago, to fit thermostatic valves, after running a system cleaner and flushing 3 times (as per instructions) the water was crystal clear (not that it was very dirty), yesterday I was in the loft and noticed in the header tank that there is what I can only describe as some kind of slime around the edge of the tank at the water level. Very odd, never had that before I wonder if it has anything to do with the protector stuff, which is one I got from Wicks - Kilrock Advanced Central Heating Protector??
What is the best product or course of action to deal with this?