CH header tank?

[Matthew]

Hi All,

I know its yet another plumbing question but we seem to have had a few issues recently since we moved into our house...

The overflow from the loft was dripping as the CH header tank ball valve had perished. I replaced it and cleaned out the tank which was full of the usual brown slurry, a couple of mm at the bottom. I added fernox. Thought all was well.

Went back into the loft last night and found brown water again. As far as I can tell the system is not overpumping through the vent certainly not whilst Ive been there. We do have a large CH layout and therefore tend to run the boiler near max. I did wonder whether an explanation may be that when the demand is for DHW rather than CH the water is boiling up throught the vent. I have noticed condensation above the CH header tank. Any words of wisdom?

BTW Can any one recommend a supplier of circular lids for the header tanks. Both are just covered with polystyrene at the moment?

Thanks, Matthew

[Dave Liquorice]

It's a "feed and expansion" tank. The water in the primary system expands as it gets hot this will lead to water from the system getting into the tank. We have a large system, the big oil fired boiler holds 12 gallons, the rest of the system is essentially 2 x 3 bed houses. I fitted a 30 gallon expansion tank and the level in that changes by an inch or three between hot and cold.

Not good. Fit a tight fitting lid. Try a local plumbers or builders merchants. Might be useful to see if there is a lable on the side of the tank giving makers name and tank code/size.