Clues that point to a leak under the slab
Confirming it yourself, safely
None of these steps opens anything up. They simply tell you whether water is escaping.
Turn off every fixture
Make sure no toilets are refilling, no irrigation is running and the ice maker is idle.
Read the meter
Look at the meter box near the curb. If the small dial or triangle still turns, water is going somewhere.
Close the water heater's cold inlet
If the meter stops moving, the leak is likely on the hot side. If it keeps moving, the cold side or the main line is more likely.
Decide whether to shut off the main
If water is surfacing indoors, close the house shutoff and keep it closed until a plumber arrives.
How plumbers usually find slab leaks
Leak detection on a slab is about narrowing the search before anyone cuts concrete. Plumbers commonly isolate sections of piping and pressure-test them, then use acoustic listening equipment to hear the leak through the floor. Some also use thermal imaging to trace a warm line under tile.
Ask the plumber to explain how they located the leak and how confident they are of the spot. A good diagnosis can save a lot of flooring.
Spot repair through the slab versus rerouting
Spot repair (open the slab)
- Cuts concrete at the leak and repairs that section
- Keeps the original pipe route
- Flooring in that area has to be removed and replaced
- Other aging sections of the same line stay in place
Reroute (abandon the old line)
- Runs a new line through walls, attic or ceiling
- Avoids breaking the floor
- Drywall openings need patching
- Often chosen when the copper shows wear in more than one spot
What drives the scope (not the price)
- Line affected
- Hot or cold, and how long the run is
- Floor covering
- Tile, hardwood, carpet or polished concrete
- Access for a reroute
- Attic space, wall depth and ceiling finish
- Pipe condition
- One isolated pinhole or widespread thinning
- Permits
- Some rerouting or repiping may need one; check with the city
Questions to ask before agreeing to a repair
- How did you pinpoint the leak, and how sure are you of the location?
- Would you recommend a spot repair or a reroute here, and why?
- What has to be opened up, and who restores flooring or drywall?
- Is there evidence of other weak spots in the copper?
- Does this work require a permit?
Common questions
Is a slab leak an emergency?
If water is surfacing indoors, yes; shut off the water. A slow leak found by the meter test is urgent but often can be scheduled for the next day with the main closed if needed.
Can a slab leak damage the foundation?
Water escaping under a slab over time can affect the soil and flooring. That is one reason to find and stop it promptly.
Why do older Fullerton homes get slab leaks?
Many were built with copper lines in or under the slab. Decades of hard water, movement and wear can lead to pinholes.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.