"oh" wrote in message
...

My En-suite basin cold tap does this also. It is because both hot and
cold pipes are close together under the floor so the heat from the hot
pipe heats up a short section of cold pipe and therefore the water
inside.

I was thinking that at first but it doesn't matter which tap I run and it
happens even when the central heating is off and I haven't ran any hot
water taps.

Has this just started or have you had a plumber in recently?

And if I turn off the water at the mains and open a cold water tap, the
water from my hot water tank eventually drains out through the cold
water tap.

Have you actually done this, i.e. EMPTIED the hot water cylinder via a
cold tap? Sounds a bit strange and costly IMO.

Yep. If I were to want to do a plumbing job on the cold water side these
days, I'd have to turn off the water at the mains, open a cold water tap,
and wait for the content of my hot water cylinder to have drained through
the cold water tap. Bizarre and annoying..

I assume you have a normal gravity fed HW system as you have a cylinder in
an airing cupboard or the loft? If so can you not just turn off the main
stopcock and the cold feed to the cylinder then the water in the storage
tank cannot empty into the cylinder so the hot water within is not 'forced'
out to your taps?


Shouldn't there be some kind of non-return valve ensuring that the hot
water doesn't drain back into the cold water side???

Are your taps in question mixer type or two individual pillar taps?

They are individual taps, apart from in the kitchen which is the usual
mixer. Doesn't matter where I experiment, same result :-( ...


John