Tracer Gas Leak Detection
Tracer gas is the method we reach for when a leak refuses to be found any other way: deep buried supply pipes, drained-down systems with nothing to hear, plastic pipework that transmits no sound, or leaks masked by background noise. It is the most sensitive tool in the kit, capable of revealing a pinhole that loses only a few litres a day.
How tracer gas works
The pipe under test is drained and charged with a trace gas, a mixture of 5% hydrogen in 95% nitrogen. Hydrogen is the smallest molecule there is: it escapes through the leak, rises vertically through soil, sand, screed and most floor coverings, and is picked up at the surface by a highly sensitive detection probe measuring parts per million. Where the reading peaks, the leak sits directly below.
Is it safe?
Yes. The 5/95 hydrogen and nitrogen mix is classified non-flammable, well below hydrogen's flammability threshold, and is non-toxic and inert. It is the industry standard trace gas used on water mains, heating circuits and even food-industry pipework. After the test the gas simply vents to atmosphere. Nothing is left in your system.
Where tracer gas beats everything else
- Buried external supply pipes: driveways, gardens and long private mains where acoustic signals fade
- Plastic pipework (MDPE, PEX, polybutylene), which carries almost no leak noise for acoustic equipment to hear
- Drained or depressurised systems: no water means no sound and no thermal signature, but gas still works
- Very small seeps: weeping joints too slow to create an acoustic or thermal signature
- Flat roofs and wet rooms: tanking and membrane failures can be traced the same way
Tracer gas surveys are usually combined with acoustic detection and thermal imaging in a single visit, so the leak is cross-confirmed by two independent methods before anyone lifts a slab.