"oh" wrote in message
...
Small plumbing snag: occasionally there's a bit of hot water coming out of
my cold water taps: I open a tap, the water runs cold for a few seconds,
then suddenly hot for another few seconds, and then cold again.

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.

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.

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?

John