Thermal imaging finds warm water. On a heating pipe under a screed, a leak shows up as a warm plume on the camera long before it shows up as a damp patch, and we can trace the run without touching the floor. Acoustic detection finds the noise a pressurised leak makes escaping — it works on cold mains where there is no temperature difference to see. Tracer gas goes in where both of those come up short. Between them we can normally put a cross on the floor within an inch or two, and then lift one board.
The most common call we get on the Victorian stock is not a burst. It is a slow leak on a heating pipe that has been going for months under a floor, showing up as a heating system that keeps losing pressure and a filling loop somebody has got into the habit of topping up. Every top-up brings fresh oxygenated water into the system, which corrodes it from the inside. If you are refilling your boiler more than about once a year, you have a leak, and the leak is doing more damage than the water you can see.
On the terraces in Sale and Altrincham, party walls make this harder and more urgent. Water tracks along a joist and comes out in next door's house, which turns a plumbing job into a neighbour conversation. Finding it accurately matters twice as much when the damage is not on your side of the wall.
A note on soft water, because it cuts both ways here. Trafford water is soft, which means no scale — but soft, low-alkalinity water is slightly more aggressive to old metals. On pre-war houses we look for two things: lead on the incoming main, and pinhole corrosion in old copper. Both are more common here than in hard water areas, where a layer of scale ends up protecting the pipe from the inside.
