John wrote:
"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?

It's actually a complete re-plumbing job and it doesn't have a gravity
feed, the problem is that several sets of plumbers were in on different
stages and I didn't get in again until a couple of months after it was
all done and appeared to be working OK :-( ...