Trace gas comes after pressure testing confirms a leak -- when acoustic tools cannot find the break because the signal is too weak, the noise too high, the pipe too deep, or the surface won't let probes reach it.
Learn the H.U.N.T.E.R. Method →Trace gas should be used after a plumbing line is confirmed as leaking through pressure testing, and the break location cannot be found with acoustic equipment. Specific situations where trace gas is most valuable: the acoustic signal is too weak for equipment to detect; environmental noise is too high; physical access prevents probe placement; the pipe is very deep; or the break is in grass, soil, or heavily vegetated areas where acoustic tools consistently fail. A small-hole technique in hard surfaces improves gas escape and keeps the search area focused.
The sequence matters. Pressure testing confirms which circuit is leaking. Acoustic listening attempts to find the break. Trace gas is brought in when acoustic methods cannot provide a clear enough answer.
Using trace gas before confirming a failed line wastes gas, risks contaminating the test area, and produces unreadable results. The gas needs a confirmed leak path to follow -- otherwise the technician is sweeping a deck looking for a leak that may not even be in the plumbing.
When working over concrete, pavers, or travertine, drilling or punching a small hole in the hard surface directly above the suspected pipe path allows trace gas to escape more easily and gives the sniffer a clean detection point.
This technique serves two purposes: it reduces the amount of gas needed to get a readable signal, and it prevents flooding the surrounding area with excess gas. When too much gas builds up and spreads through a wide area, the sniffer triggers indiscriminately -- making it impossible to isolate the actual break location.
A small, targeted hole keeps the test precise. The gas escapes where you want it to, not everywhere around it.
Gas escaping from a broken pool pipe moves upward through soil, but it follows the path of least resistance. It may travel through paver joint sand, travertine setting bed, concrete cracks, expansion joints, or along drainage paths before reaching the surface.
This means the sniffer may trigger at a point that is not directly above the break. The gas reading is a narrowing tool -- it identifies the likely zone, not always the exact cutting point. The technician must combine the gas reading with the confirmed pipe route, acoustic results, and surface clues to determine where to cut.
Identify which isolated plumbing line is losing pressure. This is mandatory before trace gas is introduced. The gas needs a confirmed leak path -- otherwise the test has no clear purpose.
Use a ground microphone, pipe microphone, or hydrophone along the confirmed pipe route with controlled air or an air/water mix. If a clear signal progression is found, the break location may be established without needing trace gas.
Move to trace gas when: acoustic signal is too weak, environmental noise is too high, probe access is impossible, or the pipe is too deep.
Introduce trace gas into the isolated line at controlled, conservative pressure. Sweep the sniffer slowly along the expected pipe route and likely gas escape paths. On hard surfaces, consider drilling a small hole above the pipe path to give the gas a direct escape route and keep the detection area focused.
On grass, soil, or vegetation, sweep methodically -- the gas will surface through the ground naturally and the sniffer works well in these conditions.
The strongest trace gas reading -- combined with the pipe route, pressure test result, and any acoustic or moisture evidence -- defines the recommended cut or access location. Document all evidence and limitations before any demolition or stone removal.
Gather water-loss history and site clues. Ask whether the suspected area is under hard surfaces, grass, vegetation, or heavily wooded -- that determines which locating tools apply.
Map the confirmed failed circuit, pipe route, deck material, soil conditions, expansion joints, drainage paths, and wind exposure before introducing any gas.
Pressure test first. Attempt acoustic locating. Move to trace gas when those methods cannot provide a clear enough answer.
Introduce gas at controlled pressure. Sweep slowly. Use the small-hole technique on hard surfaces to focus escape and reduce area contamination. On soil and grass, sweep systematically.
Mark the strongest supported location. Account for gas migration. Combine gas readings with pipe route, acoustic signal, and moisture evidence before marking a cut.
Recommend targeted access where evidence supports it. Pressure test the repaired line after repair is complete. Document all evidence and limitations.
Uses trace gas as the first tool. Does not confirm the failed circuit first. Floods the area with too much gas. Sniffer triggers everywhere. Cannot isolate the actual break location. Recommends cutting based on an unreadable, contaminated test.
Confirms the circuit with pressure testing. Attempts acoustic locating first. Uses trace gas when acoustic tools cannot provide a clear answer. Drills a small hole in hard surfaces to focus gas escape. Sweeps methodically. Combines gas readings with the full evidence picture before marking any cut.
Jeff David is the founder of Leak Business Academy, LLC and Leak and Subsurface Locators, LLC. He is a licensed pool contractor in Florida and an FSPA Palm Beach board member. Jeff teaches the H.U.N.T.E.R. Method -- including the three-tool locating sequence (pressure testing → acoustic → trace gas), the small-hole technique for focused gas escape on hard surfaces, and why trace gas is especially valuable on grass, soil, and vegetation where acoustic equipment consistently fails.
LBA training covers pressure testing, acoustic locating, and trace gas as a complete three-tool workflow -- including when to use each, how to combine them, and how to document the evidence behind every cut recommendation.
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