Underfloor heating leak under new screed in Nottingham
Acoustics and tracer gas were both misled by the way the pipes were laid. Warm water and a thermal camera showed the real pipe route and a faint mark at the leak.
- Location
- Nottingham, Nottinghamshire (NG17)
- Property
- House under construction
- System
- Wet underfloor heating on a manifold, screed laid, no boiler connected yet
- First sign
- Pressure test showed a leak on one underfloor heating circuit
- Engineer
- Adam Regan, ADI Leak Detection
- Outcome
- Leak located; repaired by the site plumbers
What was happening
The house was still being built. The underfloor heating pipes had been laid as separate runs from a manifold and the concrete screed poured over them, but the system had not been commissioned and there was no boiler.
A pressure test confirmed one circuit was leaking. The engineer was told the leak was probably in the middle of the room.
How the leak was traced
Pressure testing
The plumber on site isolated the other runs on the manifold. The test confirmed the leak was on the remaining circuit.
Acoustic listening
Picked up leak noise, but the pipe runs were laid in a ring, so the sound travelled along the pipe and could not be narrowed beyond the general area.
Tracer gas
Gave quick readings near the window, but the gas was escaping at the sides of the room. Opening a corner of screed showed it was travelling along a small channel beside the pipes.
Thermal imaging
With no boiler, hot water was run through the pipes by hand. The cold screed gave enough contrast to see the pipes: they ran down the left side of the room, not the middle. A faint thermal mark showed the leak point.
What was found
The leak was on the underfloor heating pipe, in the middle of the left-hand side of the room, where the thermal camera showed the faint mark.
The plumbers on site opened the screed at that point, confirmed the leak and repaired it.
What happened next
The repair was carried out by the plumbers on site, not by ADI.
Why one instrument is never enough under screed
Each method can be fooled by how pipes are laid in screed. Sound travels along a ring of pipe and gas follows channels in the concrete. The answer came from checking one method against another until they agreed.
Photos from the job
Pressure test on the isolated circuit. 
Tracer gas fed in at the manifold. 
Thermal image after hot water was run through the pipes. 
The damaged pipe, exposed in the screed.
Case published by ADI Leak Detection. Photos taken by the engineer during the investigation.
