Hi all
Looks like the rough builders have done me a favour!
As part of some insurance work, builders were removing loose concrete capping over hot and cold pipes ready for re-concreting. I was fair cringeing when I saw the guy levering down on the pipes to loosen the concrete. Sure enough, a minute or two later, the channel containing the pipes started to fill with warm water. Turned off the hot water, mopped up as much as possible and waited for their plumber to appear. Cut out the section where the guy had been working, capped the end off and turned on the hot water - surprised to see the channel again filling with water - the leak was futher back under the undisturbed capping. Turned off water and broke out much more capping to find a longitudinal crack in the hot pipe about 2" long. Now we have had numerous leak detection experts looking for a source of damp in this room and the source was put down to the patio door not being properly sealed. Seems that the real culprit was this pipe. But how it had contained water at all with this level of fault is a mystery. For months, the end of the channel in which it sits has been exposed and remained bone dry! So both hot and cold main runs have been replaced and hopefully we can put the room back together and forget it now.
Just thought I'd share
Phil