We have a Potterton "Netaheat" central system, just a couple of day's ago out hot water to the bathroon has turned a brownish colour...I have drained the hot water tank untill it runs clear cold water, but when I turn the boiler back on...the hot water starts to go browish again, Why?...also is this bad for your health as we have to wash in it?
Also when the boiler switches of the pump in the upstairs cupboard still runs all the time.

Alan Pellatt, January 2008

It could also be that the coil inside the cylinder has punctured through corrosion, which would let the central heating water mix with the domestic water, check to see if an overflow is dripping all the time, this is an obscure one. Also check the vent pipe in the loft from the boiler is not over the cold tank for the cylinder, this might explain the pump running over( which i think is a wiring fault) it could be pumping central heating water into the cold tank which feeds the cylinder.Not good!

PAUL KELLY, January 2008

Brown water usually comes from the incoming water main - especially if the underground pipes are steel rather than the newer plastic. However, you'll find that your loft header tank has a fair bit of sediment in it and to clean it out it really needs to be disconnected and washed out with a hose pipe.
There is also a fair chance that the copper cylinder has also sediment in it, but there's a lot more work involved to disconnect that.....I get this fairly frequently and it hasn't done me any harmmmmmmm (!) and I just put up with it. The pump doesn't need to run all of the time (but it may have a hot water run down period) and I'd suggest it isn't wired up correctly.

John, January 2008