Hi,

I'm new and have tried searching for the answer but it seems my problem
is too basic!

We noticed one of the the down pipes for the guttering was growing a
kind of mould, due to a constant supply of water running down it (and a
few plants growing in the gutter!).

I've traced the problem to the overflow for a small cold water tank in
the loft. It seems that the tank is warped and the water level is now
just over the overflow pipe.

Firstly what is this small tank for? The water in there seemed 'old'
and had sediment in the tank (which was easily stirred up just by
experimenting with the ball cock). I run all the water in the house
and couldnt make the tank empty as it all came from the huugae cold
water tank next to it. (this tank is about the same size as a toilet
cystern)

Secondly how to I go about adjusting the ball cock level so that it no
longer 'leaks'.

I noticed on this site everyone says 'find the outside water supply tap
before touching anything'. What am I look for here, a small man hole
cover?

Any help is much appreciated!!!

Cheesey Toastie