Under-Slab Plumbing Testing in McKinney and Collin County
Hydrostatic test $275 to $425; isolation and repair quoted after the test
A leak under the slab is the one cause of foundation movement that piers cannot fix. Water from a cracked drain line soaks the clay in one spot, the clay swells, and the slab heaves above it. Or the water washes the base out and the slab drops. Either way, the house keeps moving until the leak is found.
When a test is called for
- The floor survey shows a high spot or a low spot in the middle of the house rather than at the edges.
- There is a warm spot on the floor, a musty smell, or a water bill that climbed.
- Drains are slow in more than one room.
- The house has cast iron or clay drain lines, which corrode and shear as the slab moves.
- A foundation repair is planned or was just finished.
- A buyer's inspector or an engineer requested it.
Most Collin County homes built since the late 1960s are slab on grade, with post-tension slabs the norm in subdivisions built since the 1990s, while pier-and-beam survives in the pre-1960s blocks near the old downtown squares, McKinney and Plano among them, and on farmhouses outside town. Homes from before the mid 1970s often still have cast iron drain lines under the slab.
Hydrostatic test and leak isolation
The plumber opens the sewer cleanout and inserts an inflatable test ball past the house. The drain system is then filled through a tub or shower until water reaches slab level. The level is marked and watched. Holding for 20 minutes means the drain lines under the slab are intact. A drop means water is leaving the system somewhere under the house.
The test checks drain lines only. Supply lines are tested by shutting every fixture and watching the meter. A supply leak under the slab is usually a hot water line and shows up as a warm floor.
A failed test says there is a leak. It does not say where. Isolation testing plugs each branch line in turn and refills, narrowing the leak to one line. A camera on a push cable then finds the break, a bellied section, or a joint pulled apart by slab movement.
Repair
Most under-slab repairs in Collin County are done by tunneling. A crew digs a tunnel from outside the foundation to the break, replaces the line, and backfills the tunnel. The slab, flooring and walls stay intact. Where the break is close to an exterior wall or under a garage, cutting the slab can be quicker and cheaper. The quote lists both when both are options.
Supply line leaks are often rerouted through the attic instead of tunneled.
Coordination with foundation repair
The sequence matters. A heaved slab from a leak needs the leak fixed and the soil allowed to dry before anything else. A settled slab needs the leak fixed, then piers, then a retest. We schedule the plumbing and the pier crew together so the house is tested before the lift and again after the holes are backfilled. Texas does not license foundation repair contractors, so there is no state license number to check for pier work. The licenses that matter are the engineer who seals the plan, licensed by the Texas Board of Professional Engineers and Land Surveyors, and the plumber who runs the hydrostatic test. Our crews are insured and work under both.
Cost
A hydrostatic test is $275 to $425. Isolation and camera work are quoted after the first test. Tunnel repairs are priced by the foot of tunnel and the length of pipe replaced, and the repair itself goes on the plumber's permit.
Keep your last few water bills handy when you call (972) 645-5576. A climbing bill plus a warm spot on the floor tells us which test to run first.