Our Slab Leak Detection Process

Finding a leak under a concrete slab is detective work, not demolition. The goal is simple: find the exact spot where water is escaping, without breaking your floor to look for it. Here is every step of a slab leak detection visit, explained in plain English, so you know what is happening in your home and why.

Before the visit: what you can do

You can often confirm you have a hidden leak before anyone arrives. Turn off every faucet, the dishwasher, the washing machine, the ice maker and the sprinklers. Find your water meter, usually in a box near the street, and write down the reading or take a photo of it. Wait one to two hours without using any water, then read it again. If the number moved, water is going somewhere.

If water is coming up through the floor, or you smell sewage, don't wait: shut off the main water valve and call. When you call, it helps to say when you first noticed the problem, whether any floor feels warm, and how old the home is. That tells the plumber which lines are most likely involved before they even arrive.

Step by step

The nine steps of a slab leak detection visit

Listen and look first

The plumber hears what you've noticed and walks the home to look for clues.

The visit starts with a conversation. You'll be asked what you've noticed: a higher bill, a warm spot, damp carpet, the sound of water, a sewer smell or new cracks. Then the plumber walks the home, looking at where the water heater sits, where the bathrooms and kitchen are, and where the main line enters the house. Those clues show how the pipes are likely laid out under the slab. Warm or damp spots are noted, and floors are checked with a moisture meter where something looks off.

Rule out the easy causes

Toilets, faucets, irrigation, the water heater and the AC drain are checked so you don't pay to search for the wrong leak.

Before anyone looks under the slab, the common above-ground culprits are ruled out. A running toilet, a dripping outdoor faucet, a sprinkler valve, a leaking water heater or a softener stuck in its cycle can all make a meter spin. So can an AC condensate line that's tied into the plumbing. Checking these first takes only minutes, and it means you never pay for slab leak detection when the real problem is a toilet flapper.

Confirm the leak with the meter and a pressure test

A meter test and a pressure test prove water is escaping from the plumbing.

With every fixture off, the plumber watches the meter's small leak indicator, a triangle or dial that spins at even the smallest flow. Then a gauge goes on a hose bib or laundry connection to measure the pressure in the system. If the pressure drops with everything off, a pressurized line is leaking. This step turns a suspicion into a confirmed leak, and the rate of the drop gives a first idea of how big the leak is.

Isolate the leaking line

Hot, cold and branch lines are separated so the search focuses on the one that's leaking.

Most homes have several water lines under the slab: the main line in, the cold lines, and the hot lines that leave the water heater. Closing the cold inlet at the water heater shuts off the hot side, so if the meter stops, the leak is on a hot-water line. If it keeps moving, it's on the cold side. Lines can then be capped and pressure-tested one at a time, and on PEX homes each run can be tested from the manifold. By the end of this step, the search area shrinks from the whole house to one line.

Test the drains, if needed

Drain leaks don't show on the meter, so they get their own hydrostatic test and camera check.

A broken drain only leaks when water runs down it, so it never shows on your meter. If there's a sewer smell, slow drains or a damp area near a bathroom with a normal meter test, the drains are tested. In a hydrostatic test, a test ball seals the main drain at the cleanout, the system is filled with water up to slab level, and the level is watched. If it drops, a drain is leaking. An isolation test, which blocks off one branch at a time, and a camera run through the pipe then narrow it down to the broken section.

Trace the pipe's route

An electronic locator maps where the leaking line actually runs under the floor.

Pipes rarely run in the straight lines you'd expect, and original building plans are often wrong. An electronic line locator sends a signal along metal pipe, or along a tracer wire in plastic pipe, and a receiver follows it across the floor. The plumber marks the route with tape. Knowing exactly where the pipe runs means the listening and imaging in the next step happen right above it, not a few feet off.

Pinpoint the exact spot

Acoustic listening, thermal imaging and tracer gas find where the water is escaping, and two methods must agree.

This is where the leak is found. With the line pressurized, an acoustic ground microphone listens through the concrete in a grid along the marked route; escaping water makes a hiss that is loudest right over the leak. On hot-water lines, a thermal camera shows the warm patch spreading from the leak. For very quiet leaks or plastic pipe, the line is filled with tracer gas, a safe mix of about 5% hydrogen and 95% nitrogen, which rises through the slab where a detector picks it up. A good technician doesn't rely on one reading. The spot is marked only when two methods agree.

Scan the slab and mark the leak

The slab is checked for steel tendons and rebar, and the leak is marked on the floor.

Many Texas homes are built on post-tension slabs, with steel cables under high tension inside the concrete. Before anyone ever cuts into a slab, its tendons and rebar should be located. The plumber scans the marked area and notes anything in the way, so whoever opens the floor later knows exactly where it's safe to cut. The leak is then marked on your floor with tape or a removable marker, along with the line's route.

Get your written report

You receive the leak's location, the line, the readings and photos in writing.

Before the plumber leaves, you get the results in plain language: which line is leaking (hot, cold or drain), where the leak is, how it was confirmed, and photos of the readings and the marked spot. Keep this report. Your insurance adjuster will want to see it, many Texas water utilities ask for proof of a hidden leak before giving a bill credit, and it gives the plumber of your choice the exact location to work from.

How long it takes and what it costs

Most leaks are located in two to four hours. A large home, more than one leak or drain testing can take longer. Slab leak detection typically costs $150–$600, and you get the price before the visit. You pay for the testing, not for broken concrete.

What happens after the leak is found

We only do slab leak detection. Once the leak is found, you decide what to do next and who does it. Because the exact spot is marked, any repair can start with a small, precise opening instead of a search. If you plan to file an insurance claim, call your insurer before work begins and share the report. If your water utility offers a leak credit, ask about its deadline right away; some Texas cities require the request within 20 or 30 days of finding the leak.

Why this process works

Every step narrows the search. Ruling out easy causes keeps you from paying for the wrong job. Isolating the lines turns a whole house into one pipe. Tracing the route puts the tools right over that pipe, and using two pinpointing methods means the mark on your floor is backed by more than one reading. The result is the thing that matters most to you: an exact location, found without guesswork.

Water coming up through the floor?

Shut off the main water valve and call now. We’ll connect you with a licensed slab leak specialist.

Call (000) 000-0000