Damp or burst pipe???

26 Sep 2021
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United Kingdom
ABAA4CEA-93B2-441C-9E82-8EEABBC082F5.jpeg 2345A7F3-5CB2-4490-9A67-FA0C48749385.jpeg EB659132-B7C8-4720-9F21-1DCF89D6DD85.jpeg We had this downstairs toilet room fitted 4 years ago. No problems until now, and no other damp anywhere, just this patch that’s between the toilet pipe and the sink unit.
Who should I call? Damp specialists want a lot of money for a full survey, so should I call a plumber first?
my guess is (and it’s a total guess), that the pipe is leaking in the wall. no problems on the outside of the wall.
this stared a week ago. I wiped the mould away and it’s back like this after just a day.
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If you mean that peculiar S shape, might there possibly be a pipe there, buried in the plaster?

It will not be a copper pipe that shape, perhaps a plastic one. If I am correct, then it is probably a cold water supply pipe and when water is drawn it and the wall will go cold, attracting condensation and mould growth.
It might be shown with a moisture meter - cost certainly outweighs cost of plumber or damp specialist initially. It could even just be condensation. Any of the toilet pipes wet?
Thanks for your reply. no, the pipes aren’t wet. And as it’s a downstairs loo and we’ll ventilated it not prone to condensation
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Have you considered carefully chipping away at the damp area with a blunt chisel, to expose the pipe (or lack of pipe)?
From these results you can easily determine if there's a leak or not, and if the damp patch follows the line of the pipework.
With that information it would be much easier to call in the correct trade to restore full working order.
@Harry Bloomfield. I hadn’t considered the shape. As we haven’t had any problems before do you think that the plastic pop would be leaking?
@Harry Bloomfield. I hadn’t considered the shape. As we haven’t had any problems before do you think that the plastic pop would be leaking?

No - it is probably just goes cold, when water is run through it causing condensation on the wall. You could perhaps add an insulated panel over that area to help prevent it, or dig the pipe out and insulate the pipe.

Any pipe which has cold water running through it, will condense moisture out upon it.
Other option is to get a leak detection survey, cost may be covered on your insurance if you have 'trace & access' cover too. Worth checking your policy.
if you think it might be condensation, tape a sheet of clear plastic tightly to the wall over it.

If water forms on the room side of the sheet, it's condensation coming from the air.

If water forms on the wall side, it's coming from the wall.

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