Slab leaks in Houston: signs, detection and repair

Why slab leaks are a Houston problem

Most near-surface soils in Greater Houston are expansive clays, chiefly the Beaumont Clay, with the Montgomery Formation to the north and west. A 2008 University of Houston CIGMAT presentation describes these clays as having moderate to high shrink-swell potential. Seasonal moisture changes can reach 15 to 20 feet or more below the surface. It also notes that differential movement can rupture underground utility pipes connected to a slab.

Put simply, a wet season and a drought can move the ground under your house, and the water supply and drain pipes in or under the slab move with it.

Warning signs

• A water bill that jumps without any change in how you use water
• The water meter dial moving when every fixture and appliance is off
• A warm spot on the floor, which can mean a hot water line is leaking
• Damp or buckling flooring, or a musty smell with no visible source
• The sound of running water when nothing is on
• Low water pressure throughout the house
• New cracks in floors or walls (often soil movement itself, which is worth checking)

The meter test. Turn off every faucet, appliance and irrigation zone. Note the meter reading or watch its leak indicator for 15 to 30 minutes. Movement means water is going somewhere.

How a leak is found

A plumber typically isolates the hot and cold supply lines and pressure-tests each one to see which is leaking. Then they pinpoint the spot using acoustic listening equipment, thermal imaging for hot lines, or similar tools. Drain lines under the slab are usually checked with a camera or a hydrostatic test. Ask what methods the company uses and how accurate it expects the location to be. That determines how much concrete or flooring may come up.

Repair options to compare

Option	What it involves	Worth asking
Spot repair through the slab	Cut the floor at the leak, repair the pipe, patch the concrete	Who restores the flooring, and is that in the price?
Tunneling	Dig under the slab from outside to reach the pipe	Is this practical for a leak far from the edge?
Reroute	Abandon the leaking line and run new pipe through walls or the attic	Does this solve future leaks on the same line?
Repipe	Replace most or all supply lines, usually overhead	Is the rest of the pipe failing too, or was this a one-off?

Under Houston’s plumbing code amendments, galvanized pipe may not be used in or under slabs. Replacing pipe, as opposed to only fixing a leak, needs a permit pulled by a city-registered master plumber. Get the permit number.

Money matters

• Water bill credit. The City of Houston credits water lost to “excusable” leaks, including those from settlement, corrosion and wear. The credit is 100% if repaired within 30 days, 75% within 60 days, and 50% after that. Attach the plumber’s bill showing the date, address, repair type and cost. A 2023 ordinance lowered the leak-adjustment threshold to $1,000, or $100 for eligible elderly customers.
• Insurance. The Texas Department of Insurance notes that most homeowners policies cover “sudden and accidental” water damage. Coverage for the pipe repair and for slab access varies by policy, so call your insurer before work starts.
• Estimates. Texas’s plumbing board doesn’t regulate prices. Get written estimates that separate leak detection, the repair, and restoration.