Trace gas locates confirmed underground leaks by detecting where pressurized gas escapes through a pipe break. And it does something most people do not know: it also produces a dramatically better acoustic signal than a compressor alone.
Learn the H.U.N.T.E.R. Method →Trace gas leak detection is an advanced method used after pressure testing confirms a specific underground pool plumbing line is leaking. The isolated line is charged with a detectable gas -- helium or a hydrogen/nitrogen mix -- and a gas sniffer is used to detect where gas escapes through the break. The gas also produces a significantly better acoustic signal than compressed air alone, allowing a two-person team to run the sniffer and an electronic listening device simultaneously for dual confirmation. Jeff David prefers hydrogen/nitrogen mix because helium supply is limited, expensive, and sometimes unavailable.
Acoustic leak detection uses a hydrophone, ground microphone, or pipe microphone to listen for sound created by escaping water or air. Trace gas detection uses a gas sniffer to detect escaping gas molecules at the surface. These are different tools, different methods, and different types of information.
However -- and this is important field knowledge -- trace gas also produces a much better acoustic signal than a compressor. The gas escaping through the break creates a distinctive sound that electronic listening equipment can detect more clearly than water or compressed air alone. When two people are on the job, one can run the sniffer while the other uses the XLT-17, XLT-30, or LeakTronics LD-1000 to listen acoustically at the same time. This dual-method approach provides two simultaneous signals pointing to the same location.
Isolate the suspect line. The line must be isolated from the rest of the plumbing system before any gas is introduced.
Pressure test the line. Confirm the line fails -- pressure drops under controlled testing. Trace gas is only used after the leak is confirmed. Never introduce gas into a line that has not been confirmed as leaking.
Clear or reduce water in the line when needed. Gas travels more efficiently through a drier line. Depending on the configuration, reducing water in the circuit improves gas migration to the break.
Introduce trace gas at controlled low pressure. Gas is introduced through the test rig at low, controlled pressure. Do not over-pressurize -- too much gas floods the area and makes the sniffer trigger indiscriminately.
Scan with sniffer along the pipe path. Move the detector slowly along the expected pipe route -- following the map from the pipe locator, pressure test result, and acoustic evidence. Look for where the detector signal increases.
Run acoustic listening simultaneously if two people are available. Trace gas creates a significantly better acoustic signal than compressed air. With a second person using the XLT-17, XLT-30, or LeakTronics LD-1000, both methods can be run at the same time. Two signals pointing to the same location increases confidence before any cutting or digging.
Combine with other evidence before marking the cut. The sniffer reading, acoustic signal, pipe route, pressure test result, and any moisture evidence all contribute to the recommended cut location. Never mark a cut on a single reading.
Trace gas produces a much better acoustic signal than using a compressor alone. When Jeff David has two people on a job, one person uses the gas sniffer to detect escaping gas while the second person uses the Fisher XLT-17, XLT-30, or LeakTronics LD-1000 to listen acoustically for the leak sound simultaneously.
Having both signals -- gas detection and acoustic listening -- pointing to the same location provides significantly higher confidence before recommending a cut. This dual-method approach is one of the most effective field techniques for difficult underground leak locating.
Trace gas is not acoustic leak detection. Acoustic tools listen for sound. Trace gas detects escaping molecules. They are different instruments answering different questions -- though as described above, they work very well together.
Trace gas is not ultrasound. Ultrasound in pool leak detection is used in limited equipment-area situations -- finding air leaks around pumps and equipment. It is not used for underground pool plumbing leak locating.
Trace gas is not an infrared camera. Infrared cameras are useful for indoor pools, suspended pools, or pools where the structure is part of a building. They are generally not effective for outdoor residential pool leak detection.
Trace gas equipment involves pressurized gas, regulators, hoses, plugs, and specialty detectors. Anyone using trace gas must be trained and must follow all gas supplier instructions, equipment manufacturer guidelines, insurance requirements, and applicable safety rules.
Do not use pure hydrogen. Professional hydrogen trace gas systems use a hydrogen/nitrogen mixture specifically formulated for this type of work. Always verify the gas mixture before use.
Customer history and water loss pattern confirm this is an underground plumbing leak worth trace gas investigation -- not a shell or fitting defect that dye testing would handle.
Map the pipe path, the deck material, soil conditions, and wind direction before introducing gas. Know where the gas is likely to escape and what might redirect it.
Pressure test first. Pipe locating second. Trace gas third -- used along the confirmed pipe route to narrow the break location within the failed circuit.
Introduce gas at controlled pressure. Scan with the sniffer along the pipe route. Run acoustic listening simultaneously if a second person is available. Compare both signals.
The strongest sniffer reading plus the strongest acoustic signal at the same location is the recommended cut point. Document both results before any demolition.
Document the gas reading, acoustic confirmation, pipe route, and evidence chain. Pressure test after repair to confirm the circuit is sealed before closing the job.
Is trace gas the same as acoustic leak detection?
No. Acoustic detection listens for sound. Trace gas detection finds escaping gas molecules. They are different methods -- but trace gas produces a much better acoustic signal than compressed air, making them very effective when used together.
What gas does Jeff David prefer for trace gas locating?
Jeff prefers the hydrogen/nitrogen mix because it is more widely available and less expensive than helium. Helium supply can be limited, expensive, and sometimes unavailable for purchase.
Does trace gas work on every pool leak?
No. Trace gas is specifically for difficult underground plumbing leaks after pressure testing confirms the line is leaking. It is not used for shell cracks, fitting leaks, skimmer defects, or light conduit leaks.
Why does trace gas improve acoustic detection?
Gas escaping through a pipe break creates a more distinctive and detectable sound than water or compressed air alone. This makes the acoustic signal from electronic listening equipment clearer and more useful when trace gas is present in the line.
Is ultrasound used for pool leak detection?
Not for standard pool leak detection. Ultrasound is used in specific equipment-area situations -- finding air leaks around pumps and equipment -- not for underground plumbing locating.
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 prefers hydrogen/nitrogen mix for trace gas work because of consistent availability and cost. He uses a two-person dual-method approach -- one person on the sniffer, one person on the acoustic listening equipment -- because trace gas produces a much better acoustic signal than a compressor, and having both signals pointing to the same location maximizes confidence before any cutting or digging begins.
LBA training covers trace gas as part of the full evidence chain -- from pressure testing through pipe locating, acoustic listening, trace gas, and targeted excavation.
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