Why slab homes get this kind of break

In a slab-on-grade house, some supply lines were laid in the ground before the concrete was poured. Decades later, those lines can corrode, develop pinholes or wear where they rub against concrete, gravel or rebar. Ground movement and expansion and contraction of hot lines add stress.

Because the pipe is buried, a leak can soak the soil and slab for a long time before it surfaces. Sometimes it never shows above the floor at all and the only clue is the water meter or the bill.

Signs a pipe has broken under the slab

  • A warm or hot patch on tile, wood or carpet, often from a hot-water line
  • The sound of running water with every fixture off
  • The water meter's leak indicator spinning with all taps closed
  • Damp carpet pad, cupped wood flooring or loose tiles in one area
  • Moisture or a musty smell along a baseboard
  • The water heater running more often than normal
  • New cracks in the slab or water seeping at the edge of the foundation

How a slab break is found

  1. Confirm a leak exists.The plumber checks the meter with everything off and may isolate hot and cold sides to see which one is losing water.
  2. Pressure-test sections.Individual lines are isolated and pressurized to find the one that will not hold.
  3. Narrow the location.Acoustic listening equipment, thermal imaging and line tracing help mark the spot on the floor.
  4. Agree on the plan before cutting.You decide between opening the slab at the marked spot or bypassing the line, with the options and price in writing.

Spot repair through the slab vs rerouting

Open the slab and repair

  • Fixes the exact break
  • Requires breaking concrete and lifting flooring
  • Makes sense when the rest of the line is sound
  • Leaves the old under-slab line in service

Reroute the line overhead or in walls

  • Abandons the failing under-slab pipe
  • Opens drywall and attic instead of floors
  • Often preferred after more than one slab leak
  • May need a permit; check with the city

Questions to ask before anyone cuts concrete

  1. How confident are you in the leak location, and how did you find it?
  2. Is it on the hot or the cold side?
  3. What flooring will need to be removed, and who replaces it?
  4. Would a reroute avoid opening the floor at all?
  5. If you repair under the slab, what is the condition of the pipe on either side?
  6. Does this work need a permit from the City of Fullerton?

Common questions

Is a slab leak an emergency?

A fast one that floods the floor is. A slow one is still urgent, because water under a slab can damage flooring and wet the soil beneath the foundation the longer it runs. Shut the water off between uses until it is repaired.

Can I keep using water with a slab leak?

Sometimes the leaking line can be isolated so the rest of the house works. Otherwise keep the main closed except when you need water, and get it located promptly.

Will the same thing happen again?

If the under-slab lines are old and corroded, more leaks are possible. That is the main argument for rerouting after a second slab leak.

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