Slab leaks in Houston: signs, causes, and who to call

Why Houston gets slab leaks

Most Houston homes sit on a slab-on-grade foundation, a concrete pad poured directly on the ground with the water and drain lines running under or inside it. The ground is expansive clay. It swells when wet and shrinks when dry, and the slab moves with it. Pipes under the slab do not move as freely. Over years of summer droughts and spring rains, a copper line rubs against concrete or rebar until it wears through, a joint works loose, or a drain line separates.

Other causes are less common but real: corrosion in older copper from the water chemistry, a nail or rebar that nicked a line when the house was built, and pressure that runs too high because the house has no working pressure regulator.

The signs

• A warm or hot spot on the floor. This almost always means a hot water line.
• A water bill that jumps with no change in use.
• The sound of running water when every fixture and the irrigation are off.
• The water meter still turning with the main shutoff at the house closed.
• Damp carpet, cupped wood floors, dark grout lines, or mildew smell in one area.
• Low water pressure that started recently.
• New foundation symptoms: doors sticking, cracks in drywall over doors, a floor that is not level.

None of these prove a leak by themselves. Together they are enough to call a plumber.

What it is not

Not every wet floor is a slab leak. A failed shower pan, a leaking toilet flange, a drain under a tub, a sweating AC drain line in the slab, and a cracked irrigation line next to the house all look similar from inside. A plumber who tests before quoting will rule these out. A plumber who starts breaking concrete on the first visit will not.

How a plumber confirms it

1. Isolate the system. Close the main and watch the meter. Then isolate hot from cold at the water heater to learn which side is leaking.
2. Pressure test. The plumber pressurizes the supply lines and watches for a drop. Drain lines get a hydrostatic test, where the line is plugged and filled with water and watched for a drop.
3. Locate. Electronic leak detection listens for the leak through the slab. Thermal imaging helps on hot lines. For drains, a camera inspection shows the break.
4. Mark and quote. Only now does the plumber know where the leak is, what pipe it is in, and how deep.

Expect a fee for this work. Leak detection is a skill and takes equipment, and the diagnosis is the product. A typical range in Houston is a few hundred dollars. Ask the fee up front.

The three repair options

Option	What it means	When it fits
Spot repair through the slab	Break the floor and concrete above the leak, repair the pipe, pour back	One known leak, accessible spot, floor you are willing to open
Tunnel under the slab	Dig from outside and tunnel to the leak, repair from below	Leak under tile or cabinets you do not want to destroy, or a drain line
Reroute	Abandon the line under the slab and run a new one through the attic and walls	Older copper with repeated failures, or multiple leaks

A spot repair is the cheapest today. A reroute costs more now but ends the problem for that line. Tunneling preserves the inside of the house but usually costs more than breaking the floor. Ask the plumber which they recommend and why, and ask what the pipe looked like when they found it.

Permits and foundation

The City of Houston requires a plumbing permit for repipes and reroutes, and a licensed company pulls it in its own name. Ask whether the specific repair needs one. If the house also has foundation movement, the sequence matters: foundation work can break pipes, and a slab leak can cause foundation movement by softening the soil. A good plumber will tell you to get a hydrostatic drain test after any foundation lift.

Insurance

Texas homeowner policies vary. The common pattern is that the policy covers the access and the damage, meaning breaking and restoring the slab, floors, drywall and cabinets, but not the repair of the pipe itself. Some policies exclude slab leaks entirely. Some add coverage by endorsement. Call your agent before the work starts, get the plumber’s written diagnosis with photos, and keep the failed pipe section.

Why a phone quote is meaningless

Nobody knows what the repair is until the leak is found. A company that quotes a price before testing is either guessing low to get in the door or guessing high to cover every case. Pay for the test, get the written finding, and then get a bid that names the method, the pipe, what gets opened, who restores it, the permit and the warranty.