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