Split underfloor heating pipe under a home office floor, Marlborough
The circuit would not hold any pressure. Air at 2 bar could be heard escaping through a wall, and acoustic equipment followed it to one corner of the room.
- Location
- Marlborough, Wiltshire (SN9)
- Property
- Residential property
- System
- Oil-fired boiler serving underfloor heating downstairs and radiators upstairs; 22mm plastic (PEX) pipe
- First sign
- Underfloor heating circuit held no pressure at 2 bar
- Engineer
- James Bexter, ADI Leak Detection
- Outcome
- Leak found; temporary repair; part re-run in copper
What was happening
The house has an oil-fired boiler running underfloor heating on the ground floor and radiators upstairs. The underfloor heating had been isolated before the engineer arrived because the system was losing pressure.
The plastic pipes are buried in the floor, so looking for the leak was not an option.
How the leak was traced
Air pressure test
The underfloor heating pipework was disconnected and a compressor put air in at 2 bar. It held nothing, and the air could be heard escaping through the wall on the far side from the test point.
Acoustic listening
Listening along the floor surface followed the sound of escaping air to one corner of the office room.
Visual inspection
Once that corner was opened, the leak and the condition of the pipe could be seen directly.
What was found
The leak was a split in 22mm Speedfit PEX pipe buried in the corner of the office room.
What happened next
A temporary repair was made at the leak. The pipe manufacturer does not recommend permanent push-fit fittings on buried plastic pipe of this kind, so the customer was told the repair could not be warranted.
At the customer’s request, the section from the repair back through the wall to the garage was replaced in protected copper. The boiler flow temperature was turned down, and the engineer noted that automatic air vents should be fitted at the high points near the boiler.
The longer-term recommendation is to re-pipe the flow and return to the manifold in copper.
What the repair left to decide
Finding the leak kept the digging to one corner. What to do next depended on the pipe itself, and the customer was given the honest version: a temporary fix now and a recommendation for later.
Photos from the job
The underfloor heating manifold. 
The gauge at zero: the circuit held nothing. 
Acoustic listening along the floor. 
The temporary repair in the opened corner.
Case published by ADI Leak Detection. Photos taken by the engineer during the investigation.
