What's the fastest way to establish if there is an 'active leak' or not? Conflicting reports

[QuimReaper]

I'm in the process of buying a flat (Victorian terraced garden) and the only thing that caused me any alarm on the survey was the damp, so I followed up with a specialist damp and timber survey.

The damp and timber survey revealed a likely leak due to a saturated interior wall - no evidence that it's coming from pipework in the flat above and the vendors have already had a CCTV drainage survey in the last couple of years so the suspicion is that it's a mains water leak.

My vendors have responded to my survey my having two independent specialists round and reported that 'both specialists have identified the scope of work is internal only; hey assessed the scope of work to be localised damp treatment, re-plastering and damp proofing. Neither identified any evidence of an active mains water leak'

I'm a bit lost here. My damp survey was done by a specialist surveyor, whereas these opinions are from damp treatment works companies. The vendors haven't given me any kind of report or justification for the 'no reason to suspect a leak' opinion, only quotes for minor remedial works that they are willing to knock off the cost of the property.

I want to know for sure one way or another before I exchange as it seems foolhardy to take their word for it and a small (£3k) price reduction when I have a paid-for report that suggests a bigger problem.

Any advice on how to get to the bottom of it, or find a way through it as quickly as possible?

I suppose what I need to do is understand the likely cost of repairing a mains water leak (which I understand from the survey involves 'lifting up the flooring to find and locate the old lead pipe (assumed) followed by organising the entire length of pipe to be replaced with new 25mm blue MDPE by a clean water accredited plumber') and get that taken off the price as well if they want this over the line as quickly as possible, which they seem desperate to do.

Turn every tap and appliance off, then watch the water meter carefully for a while to see if it's still turning.

If you are replacing the pipework after the company stop tap or water meter anyone can replace the pipe. It’s not a major job they could do it before exchange.

@Sheep85 That's reassuring - so is it taking up the flooring (and likely damaging it in the process) that's the real pain in the ass with getting it done? That doesn't alarm me too much as it's vile and I want to replace it anyway

As suggested, turn off the taps and observe the water meter, I would also get a pressure test of the central heating, as it could also be a source of a leak.

Luis thank you - surreally, that was one of the recommendations of the report and the vendors haven't confirmed whether they've done it yet. This is a free diagnostic that would settle it and strange that they haven't confirmed if they have or not. Hopefully 'no evidence of a mains leak' means they have.

In some ways though, if they have, that leads me even more into the unknown.

Get them to fix it before buying. If they won't, walk away. You could be buying a very expensive mistake.

The problem is, you’ll never know whether they’re telling the truth or not re:switching off the water meter. I’d want £10k off as that will the cost of lifting the floors, investigating, taking the wall back to brick, possibly replacing ‘saturated’ joists/wood and all the hassle of arranging the works and living through it.

Dilemma meaning they could take a photo, switch off the meter, then take another a few hours later showing no movement?

'No evidence' doesn't mean there isn't one, just that one hasn't been found.

I don't think you can 'switch off' a water meter.

You'd need to ask for video or timestamped evidence basically. A teeny tiny leak you might not see the meter moving in a short video but you would if you compared a photo from a few hours apart.

Thanks @Flyingdolphins, I didn't think you could but was just trying to work out @Dilemma999's comment that 'The problem is, you’ll never know whether they’re telling the truth or not re:switching off the water meter'

You can switch off at the company stop tap but you need a special water key. The company stop tap is usually very close to the meter but I would still get them to sort it out. It could be a neighbours lead pipe that leaking if it’s a flat.