On Tue, 29 Nov 2016 20:26:47 +0000, Roger Hayter wrote:

mechanic wrote:

On Mon, 28 Nov 2016 01:26:40 -0800 (PST), David wrote:

I agree entirely. From the sound of it, though, the OP (and
British Gas) are well on the way to eliminating the likely
scenarios, so I thought I'd chip in with something more unlikely


That's exactly right. BG are not idiots, they know the likely
causes, and indeed we have been working to eliminate them one by
one. The trouble is we are approaching the point that serious damage
will have to be done to the flooring to pin point the leak and
repair it. There is some insurance coverage for tracing and repair
but there will be a lot of disruption to carry out the work.

I suppose it would not be possible to bypass the suspect pipes by a
separate, but permanent and cosmetically acceptable, route? Say via a
different room, or a ceiling?

As an update to the story - using a leak tracing company we found
the leak was in a radiator feed pipe in the bathroom. Fortunately
plain sheet vinyl flooring there so simple to get to the pipes. The
feed included a push-fit joint situated under one of the walls.
Using the company's camera you could see the drips from the joint!
They have a useful acoustic detector thing too - impressive
swooshing noises on pipes near the fault.

Many thanks for everyone's thoughts, and the many helpful
suggestions that helped our thinking on possible ways forward.

Plumbing now in progress to repair fault.