What Is Trace Gas Testing for Pool Leaks?

Trace gas is a specialized tool used when acoustic listening identifies an underground break area and additional precision is needed. LSL is one of the only pool leak companies in South Florida with a full trace gas system.

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When pipe testing confirms that a pool plumbing line has a break underground, acoustic listening is the first method used to locate where. The technician listens along the pipe path for the signal of the escaping air. When a general area is identified and additional confirmation or precision is needed, trace gas becomes the next step. LSL is one of the only pool leak detection companies in South Florida that has a full trace gas system -- other pool leak companies regularly call LSL specifically to use their trace gas equipment on difficult jobs.

The Gas Blend Used

Trace Gas Specifications

Blends Used
5% hydrogen / 95% nitrogen blend, and helium -- both used by LSL depending on the job
Flammability
Non-flammable at this concentration -- well below the 4% lower flammable limit for hydrogen in air
Toxicity
Non-toxic -- hydrogen and nitrogen are both naturally occurring atmospheric gases
Pool chemistry
No effect on pool water chemistry or equipment
Detection method
Surface sensor detects hydrogen molecules escaping at the break point
Why hydrogen
Smallest molecule in existence -- penetrates soil and concrete faster and more accurately than any other gas

How Trace Gas Testing Works -- Step by Step

  1. Air test confirms which line is broken

    Before trace gas is used, pipe testing has already identified which specific plumbing line is losing pressure. Trace gas is applied to that line -- not to all lines simultaneously.

  2. Trace gas is introduced into the pressurized line

    The 5% hydrogen / 95% nitrogen blend is connected to the manifold and introduced into the failing line. The line is pressurized with trace gas, which mixes with the air already in the pipe.

  3. Gas follows the path of least resistance underground

    The trace gas travels through the pipe and exits at the point of the break -- the path of least resistance. Underground, the gas rises through the soil and works its way up through concrete, pavers, or grass to the surface.

  4. Surface sensor scans above the pipe path

    The technician moves a handheld hydrogen sensor along the surface above the pipe's known path. The sensor detects hydrogen concentration in the air near the surface. The signal gets stronger as the sensor approaches the break location.

  5. Break location is marked

    When a strong hit is detected, the technician shuts the tank valve and continues sniffing while monitoring signal decay. The last location showing residual concentration is typically the origin zone. That area is marked as the general location of the break for excavation.

Why This Matters for Your Deck

The difference between excavating with and without trace gas is significant. Without a precise location, a repair crew has to cut and remove concrete based on estimation -- following the pipe path and opening sections until the break is found. That can mean removing 10–20 feet of deck to locate a break that's in a 6-inch section. With trace gas, the opening is targeted. One small cut, directly over the break. Less concrete removed, less restoration needed, lower overall repair cost.

Free Homeowner Resources from Leak Business Academy

Use these tools to understand your pool's water loss before your appointment.

Find the Exact Location Before Any Concrete Is Cut

Leak and Subsurface Locators uses trace gas on every underground pipe investigation. Call Sandra to schedule a visit.

Frequently Asked Questions

Is trace gas safe near a pool with people or children around?

Yes. The 5% hydrogen / 95% nitrogen blend is non-flammable and non-toxic. It dissipates immediately upon escaping underground -- it doesn't accumulate at the surface in any meaningful concentration. Hydrogen and nitrogen are both naturally occurring components of the atmosphere. Standard precaution is to avoid open flames near the equipment during introduction, but the gas itself presents no hazard to people or animals in the pool area.

Can trace gas find a leak if the pipe is very deep?

Yes, though depth affects the time required for the gas to reach the surface. In South Florida, most residential pool plumbing is relatively shallow -- 12 to 36 inches below the deck -- and trace gas rises through that distance effectively. Very deep pipes (below 4–5 feet) may require longer wait times for the gas to migrate upward, and the signal may be more diffuse at the surface. An experienced technician accounts for depth in how they scan and interpret the signal.

Why is hydrogen used and not another gas?

Hydrogen is the smallest molecule in existence. Its tiny molecular size allows it to penetrate soil, root systems, clay, and even partially sealed concrete much more effectively than larger molecules. It rises quickly and concentrates at the leak point rather than dispersing widely through the soil. This makes it the most reliable tracer gas available for underground pipe leak location. At 5% concentration, it is non-flammable, eliminating the safety concern that might otherwise come with using hydrogen.

Does trace gas work through concrete and pavers?

Yes. Concrete and pavers are porous materials at the microscopic level, and hydrogen molecules -- being extremely small -- permeate through them. The signal is detectable at the surface above a concrete deck when the gas has had sufficient time to migrate upward. The density and thickness of the concrete affects how long it takes, but properly applied trace gas reliably reaches the surface through standard pool deck materials.