Leak detection

How Do Plumbers Find Hidden Leaks? Leak Detection Explained

Acoustic microphones, thermal cameras, tracer gas and more. What each tool does and what to expect on a visit.

By the Arlington Leak Pros team · October 16, 2026

Acoustic leak detection equipment used by Arlington Leak Pros technicians

Leak detection is how a licensed plumber finds a hidden water leak without breaking open your floors, walls or yard. Instead of guessing, the technician uses tools that hear, see or trace the leak, then marks the spot within a foot or two. This guide explains each tool and what a visit looks like. Have a leak now? Call Arlington Leak Pros at (817) 285-5426, 24/7.

Why not just open the wall or floor?

Water travels. A leak under a slab or behind a wall can show up feet away from the broken pipe. Cutting where the water appears often means cutting more than once. Finding the exact spot first keeps the opening small, which saves money on the repair and on patching floors, drywall and tile afterward.

In Arlington, most homes sit on concrete slabs over clay soil, so a wrong guess can mean breaking concrete in the wrong room. That is why we pinpoint first and cut second.

What tools do leak detection pros use?

The main leak detection tools are acoustic listening devices, thermal imaging cameras, pressure test gauges, tracer gas, pipe locators, moisture meters and video pipe cameras. Each one answers a different question, so technicians usually combine two or three to confirm a leak before marking the spot.

Tool	What it does
Pressure test gauges	Confirm which line is leaking (hot, cold, main, irrigation)
Pipe locator	Traces where a buried or under-slab pipe runs
Acoustic microphones	Hear water escaping through concrete and soil
Thermal camera	Shows heat from hot water leaks and cool, wet areas
Tracer gas	Rises through soil or slab to reveal tiny leaks
Moisture meter	Measures how wet drywall, wood and flooring are
Video pipe camera	Looks inside drain and sewer lines

How does acoustic leak detection work?

Water forced out of a pressurized pipe makes a hiss or rushing sound. An acoustic ground microphone picks up that sound through concrete or soil. The technician moves the sensor along the pipe's path and listens for the spot where the sound is loudest. That is usually where the leak is.

Quiet homes help. During a visit, we may ask you to turn off TVs, fans and appliances for a few minutes while we listen.

What does a thermal camera show?

A thermal imaging camera shows temperature differences on a surface. A hot water leak under a floor shows up as a warm patch. Wet drywall often looks cooler than the dry wall around it. Thermal imaging is fast and does not touch anything, so it is great for scanning floors, walls and ceilings.

It works best on hot water lines. Cold water leaks are harder to see, which is why we pair the camera with acoustic gear and pressure tests.

Think you have a leak? A licensed Arlington technician answers 24/7.

Call Now (817) 285-5426

When is tracer gas used?

Tracer gas is used for very small leaks that are too quiet to hear. The water line is drained and filled with a safe, non-toxic gas mix. The gas escapes at the leak and rises through soil or concrete, where a sensitive detector picks it up. It is common for underground and pool lines.

You can read more about buried lines in our guide to underground water line leaks.

What happens during a leak detection visit?

A typical visit has five steps: the technician asks what you have noticed, checks the water meter, pressure tests to find which line is leaking, uses acoustic and thermal tools to pinpoint the spot, then marks it and explains repair options and price. Most visits take one to three hours.

Talk it through. Tell us about sounds, wet spots, bills and when it started.
Meter check. Confirms water is leaking and roughly how fast.
Isolate the line. Pressure tests show if it is hot, cold, main or irrigation.
Pinpoint. Acoustic, thermal or tracer tools find the exact spot.
Mark and explain. You see the spot and get repair options and a price.

Want to check for a leak before you call? Try the meter test in our guide to a high water bill.

How much does leak detection cost in Arlington?

Basic leak detection in Arlington usually costs about $150 to $400. Slab leak detection runs about $250 to $600, water line leak detection about $200 to $500, and pool or spa leak detection about $250 to $550. You get an exact price before any work begins.

See the full leak detection cost table on our homepage.

How accurate is professional leak detection?

With the right tools and an experienced technician, most leaks can be marked within a foot or two. Accuracy depends on pipe depth, soil, background noise and leak size. Combining tools, such as a pressure test plus acoustic listening plus thermal imaging, is what makes the result reliable.

Frequently asked questions

Is leak detection safe for my home and family?

Yes. The tools are non-invasive. Acoustic gear and thermal cameras only listen and look. Tracer gas is a safe, non-toxic mix. Nothing is cut open until the leak is found and you approve the repair.

Can you find a cold water leak?

Yes. Cold water leaks give off no heat, so thermal cameras help less. Technicians rely on pressure tests, acoustic listening and sometimes tracer gas to pinpoint them.

Do I need to be home during leak detection?

Yes, an adult should be home to give access and hear the results. You will see where the leak is marked and get a price for the repair before any work begins.

Can you repair the leak on the same visit?

Often, yes. After the leak is found, we explain repair options and the price. Small repairs can sometimes be done the same day. Larger ones, like a reroute, are scheduled.