Yesterday, 10:52 AM
It sounds like you’ve got a hidden leak in the wall, which would explain both the water pressure drop and the spreading damp patch. A leak detection specialist is the right choice, and the sooner you get them in, the better, to avoid further damage or mold. Since you’re in Belfast, look for someone who uses non-invasive methods like thermal imaging so they can locate the leak without tearing open large sections of the wall. I recently dealt with a plumbing company in the Mesa, AZ area that used these techniques, and it worked great. If the company you’ve found has strong reviews, I’d go ahead and book them. Also, take photos in case you need to claim on insurance.