On Jun 22, 3:24*pm, "neverwas" wrote:
The inlet to the attic tank is above the level of the water, though
the ballcock is letting the level go higher than it should, though not
that high.

Another elimination question. *Any toilet which is *not* fed from the
attic tank? *(Supplying WCs from a storage tank guards against siphonage
from the cistern to the drinking tap. *It is a point I keep in mind as
we have no storage tank.)
--
R

No, we have two toilets, both of which are fed from the attic tank. I
was talking to someone just now and they mentioned that if two taps
from the mains are opened, we are probably reaching the maximum
capacity of the pipe from the mains, which apparently will flush dirt
out. I guess that's a solid explanation. It wouldn't surprise me if
the dirt is from the mains as the water has always had a yellow hue to
it, especially in summer. Most probably iron/iron bacteria due to
sludge formations in toilet cistern for example.