Why slab leaks happen here
A large share of La Palma was built as single-story tract housing on slab-on-grade foundations. In those homes the copper or galvanized water lines were often laid in or under the concrete before it was poured, so a leak can develop where nobody can see it. Hot water lines are the usual suspects because heating and cooling make the pipe expand and contract against the concrete and gravel around it.
Over decades, small movements of the slab, abrasion where pipe touches rock or rebar, pinholes from water chemistry and poor joints from original construction can all open a leak. Because the water has somewhere to go, a slab leak can run quietly for a long time before anything shows on the floor.
Warning signs of a leak under the slab
- The water meter's leak indicator or dial moves with every faucet, toilet and appliance off.
- A warm or hot patch on tile, laminate or carpet, often in a hallway, kitchen or bathroom.
- The sound of running water inside a wall or under the floor when nothing is on.
- A water bill that climbs without any change in how the household uses water.
- Damp carpet tack strip, lifting wood flooring or new cracks in tile grout.
- The water heater running more often than usual, which can mean a hot line is leaking.
How a plumber confirms a slab leak
Concrete should not be opened on a guess. A careful diagnosis narrows the leak to a line and then to a spot.
Meter test
With all water off, the meter is watched for movement. If it moves, water is escaping somewhere between the meter and the fixtures.
Isolate hot from cold
Closing the cold inlet at the water heater shows whether the loss stops, which points to the hot side.
Pressure test individual lines
Lines are isolated and pressurized to see which one cannot hold pressure.
Pinpoint the location
Acoustic listening equipment, thermal imaging or line tracing is used to mark the most likely spot on the floor.
Recommend a repair
Only then should you get a written explanation of the options and the price.
Spot repair versus reroute
These are the two common ways to deal with a leaking line under the slab. The right one depends on the pipe's overall condition.
Spot repair through the slab
- Concrete and flooring are opened directly over the leak.
- Only the damaged section of pipe is replaced.
- Can make sense when the rest of the pipe is in good shape.
- Flooring and concrete need patching afterward.
- Another weak spot on the same old line may leak later.
Reroute the line
- The leaking line is abandoned in place under the slab.
- A new line runs through walls, ceilings or the attic.
- Often chosen when the line has leaked before or is badly corroded.
- Means drywall openings and patching instead of floor demolition.
- Usually requires a permit; check with the City of La Palma.
What drives the cost
- Location of the leak
- Under cabinets, tile or hardwood is harder to reach and restore than under carpet.
- Repair approach
- A single spot repair and a full reroute are very different amounts of labor.
- Pipe condition
- Thin or pitted copper elsewhere on the line can push the choice toward rerouting.
- Restoration
- Concrete, flooring, drywall and paint repair may or may not be included. Ask.
- Water damage
- Drying out walls and subfloor is a separate job from fixing the pipe.
Questions to ask before slab work
- How did you confirm which line is leaking, and how confident are you of the location?
- Would you recommend a spot repair or a reroute for this house, and why?
- What will be opened, and is patching the concrete, flooring or drywall included?
- Does this work need a permit, and will you pull it?
- What is your CSLB license number?
Common questions
Can I keep using water with a slab leak?
If the leak is small you may be able to, but water under the slab can damage flooring and the soil under it. If you see water surfacing or the meter is spinning fast, close the main shutoff and call a plumber.
Is a slab leak always on the hot side?
No, but hot lines leak more often because of expansion and contraction. Closing the water heater's cold inlet is a simple way to see whether the loss stops.
Does rerouting mean the whole house is repiped?
Not necessarily. A reroute can replace just the one leaking line. If several lines are failing, a plumber may suggest repiping instead.
General information for La Palma, not a quote or professional advice. In an emergency, call 911.