On 3 Dec 2006 07:22:29 -0800, None wrote:

To see the extent of the problem I drained the attic tank, and there
was a thick brown sludgy mess at the bottom also. I wonder is it due to
a mains leak somewhere?

A leak with several bar of pressure behind it is not likley to let any
muck in. Now if the pressure drops and becomes negative relative to the
inside of the pipe...

I'm on a mains water supply with strict regs... so I don't think this
should be happening?!

You don't say where you are. Birmingham's water is lovely and soft but is
distinctly brown, either from Elan peat and/or the iron pipes that ship
it to Birmingham from Wales.

Is the tank covered with a close fitting lid? If not then don't expect
clean tanks, even with a lid I doubt the builders will have cleaned the
tanks before fitting so a layer of brick dust and other muck is "normal".

--
Cheers
Dave. pam is missing e-mail