Following some pipework changes and draining and refilling of the cold
water tank we have fairly clear but yellow water coming from the cold
water tank in the loft. A torch will penetrate the murky tank which is
not pretty inside but is clear of dead animals, birds etc.

What had for a couple of years been a redundant run of pipework is now
used for the water run from soon after the water softener to the loft
tank. Water from the softener direct to another tap is crystal clear.

The changes were over 2 weeks ago and the water appears not to be
getting any clearer.

The central heating header tank is about a meter below the level of the
cold water tank and the level is not rising so I doubt whether the coil
in the hot water cylinder is leaking.

The galvanised cold water tank is probably 45 years old and in need of
replacement which will be organised soon.

Any ideas what could be causing the yellow water?
(References to bodily fluids are not required!)

I'm tempted to say - you must have really, really p***** off your
plumber for him to rig that up.

Realistically, once a bug gets established in stagnant pipework, it
can be really persistant. I had this in a flat where the system had
been drained down for some months, and a mate suggested I buy water
purification tablets (the travel kind) and chuck the whole packet in
the header tank. Not as effective as bleach, but a great deal safer.
Blowing the pipes through with mains pressure beforehand will help
reduce the levels too, if possible, before the chemical attack on them.

Invisible Man wrote:

Any ideas what could be causing the yellow water?
(References to bodily fluids are not required!)

Sorry, I have to disagree the
http://news.bbc.co.uk/1/hi/england/southern_counties/4717327.stm

David