What a slab leak is

In a slab-on-grade house, the floor is a concrete pad poured directly on the ground. In many homes built in the decades after World War II, copper water lines were run under or through that slab before it was poured. When one of those lines develops a leak, the water spreads into the soil and concrete below the floor.

Hot water lines are a frequent culprit because heat and expansion add stress. A hot-side slab leak is often what creates a warm patch on the floor that you can feel with bare feet.

Signs to watch for

  • A warm or hot spot on a tile, wood or concrete floor.
  • The sound of running water when every fixture is off.
  • The water meter dial moving with all water turned off in the house.
  • A water bill much higher than usual without a change in use.
  • Damp carpet, swelling baseboards or mildew smell with no visible source.
  • Cracks in flooring or tile that appear suddenly.
  • The water heater running more often than usual.

The meter test

A simple way to see if water is escaping somewhere.

  1. Turn off every fixture.Make sure no toilets are refilling, no irrigation is running and no appliance is drawing water.
  2. Read the meter.Open the meter box and look at the dial and the small leak indicator. Note the reading or take a photo.
  3. Wait and read again.After 15 to 30 minutes with no use, check again. Movement means water is going somewhere.
  4. Close the house shutoff and repeat.If the meter stops with the house valve closed, the leak is inside the house side. If it keeps moving, the leak may be in the yard line between the meter and the house.

How urgent is it?

  • IfWater is coming up through the floor or the slab is visibly wetThenClose the main and call a licensed plumber as soon as possible.
  • IfA warm spot and a moving meter, but no visible waterThenClose the main when you are not using water and book leak detection soon.
  • IfOnly a higher bill, with no other signsThenDo the meter test and check toilets for silent running first.

Repair approaches a plumber may offer

Direct spot repair

  • Opens the floor and slab at the leak
  • Fixes the exact section
  • Means flooring and concrete repair afterward
  • Other sections of the same pipe stay in place

Reroute or repipe

  • Abandons the line under the slab
  • Runs new pipe through walls or the attic
  • Avoids breaking the floor
  • May be suggested when the pipe has failed more than once

What to ask before anyone opens the floor

  1. How did you locate the leak, and how sure are you of its position?
  2. Is this the hot or cold line, and what condition is the rest of it in?
  3. What will the floor and slab look like afterward, and who restores them?
  4. Would rerouting this line make more sense than a spot repair?
  5. Will the repair need a permit from the city?

Common questions

Is a slab leak an emergency?

It becomes urgent when water is visibly coming up or damaging finishes. Otherwise, close the main when you can and arrange leak detection soon rather than waiting for it to get worse.

Does homeowner's insurance cover slab leaks?

It depends on the policy. Some policies cover access and resulting damage but not the pipe itself. Ask your insurer.

Can a slab leak damage the foundation?

Water under a slab over time can affect the soil and concrete. That is a good reason not to ignore the signs.

General information for La Habra, not a quote or professional advice. In an emergency, call 911.