A Dallas homeowner heard water moving in two bathrooms. The meter kept spinning after the valve above the water heater was closed — pointing to a cold-line leak. We marked a blue X in the hallway and tunneled 17 feet from outside so the floor never had to come up.
Real jobs teach faster than theory. This Dallas slab leak is a clear example of how meter testing, hot-vs-cold isolation, and tunneling work together. The homeowner — Hunter H. — already shared the story on our Dallas slab leak page. Here is the full walkthrough for anyone facing the same pattern.
What Hunter noticed
Hunter heard water movement in the front bathroom and the master bathroom. That sound, with fixtures off, is one of the classic signs of a slab leak. The digital flow indicator on the water meter was rotating at medium speed with the curb stop open — confirmation that water was moving somewhere in the house.
Meter test: cold line, not the heater
We closed the valve above the water heater. The meter kept rotating at medium speed. That single step matters: if closing the heater valve stops the meter, the leak is usually on the hot side. If the meter keeps moving, the leak is on the cold side (or elsewhere on the cold distribution). This is the same method described in hot line vs cold line isolation.
Finding the hallway leak
Investigation found a cold water leak under the floor in the left hallway. We marked it with a blue X. Line tracing was inconclusive in places — likely because PEX had been used during earlier remodeling, which can limit how cleanly some tracers follow a path. The leak also sat in an area where a previous leak had been repaired. Other quieter leaks cannot always be heard until the loud one is fixed.
The 17-foot tunnel from outside
Rather than break out the hallway floor, we tunneled about 17 feet under the slab from outside. That kept the finished hallway intact. Dirt came out along the exterior, the repair was made on the cold line, and the tunnel was backfilled against the brick wall when the work was done. For the method comparison, see tunneling vs breaking the slab.
What this job teaches
- Listen to the meter. A spinning indicator with everything off means water is moving.
- Isolate hot vs cold with the water-heater shutoff before you assume which line failed.
- Mark the spot. A clear floor mark keeps the crew honest about where detection pointed.
- Tunnel when floors matter. A long tunnel is often worth it to spare a hallway finish.
- Expect follow-up checks. A loud leak can hide quieter ones until it is quieted.
Staggs Plumbing is registered as a plumbing contractor in every city we serve, including Dallas. You get upfront written pricing before work starts. Financing available when a larger repair is on the table. Call (682) 284-0966 if you hear water under a Dallas floor and want the same kind of diagnosis.
Frequently asked questions
Why did closing the water-heater valve matter?
If the meter stops after that valve closes, the leak is typically on the hot side. Hunter's meter kept spinning, so we focused on the cold line.
Why tunnel instead of opening the hallway?
The leak sat under a finished hallway. Tunneling from outside repaired the cold line without breaking out that floor.
Can remodeling PEX make tracing harder?
Yes. Mixed materials and remodel PEX can make some forms of line tracing less conclusive, which is why meter tests and acoustic pinpointing still matter.
Will every Dallas slab leak need a 17-foot tunnel?
No. Tunnel length depends on where the leak sits relative to an exterior access point. Some repairs are much shorter; some are better as break-out or reroute.
Serving Plano from our headquarters on F Avenue? See Plano slab leak repair for local detection and repair details.
