Signs of a slab leak — and what to do next
8 warning signs that your home has a pinhole leak under the concrete slab. Most common in 1960s–80s slab-on-grade builds.
The 8 most-common signs
1. A warm spot on the floor (most reliable indicator — slab leaks on the hot-water side warm the slab above them).
2. Unexplained jump in your water bill of $30–$100+ in a single month with no usage change.
3. The sound of running water when nothing in the house is on (turn off everything; if you still hear it, you have a leak).
4. Moisture or a mildew smell under carpet, hardwood, or tile.
5. Low water pressure at one or more fixtures.
6. Cracks in walls or in the slab itself (slow leaks erode soil under the slab over time).
7. Mildew on baseboards or peeling paint near the floor.
8. High indoor humidity for no obvious reason (dehumidifier filling up faster than usual).
Who tends to get them
Slab-on-grade homes built between roughly 1960 and 1985 with copper plumbing poured directly into the slab. Common in the Sun Belt — Arizona, Texas, Nevada, parts of California, the Southeast — and in some Midwest 1970s ranches.
Homes with concrete-encased copper develop pinhole corrosion at the rate of about 1 leak per 12–20 years per line. Once you've had one, expect more on the same line within 5 years.
Detection and repair
Detection: $280–$480 standalone. We use acoustic equipment (listens for the leak through the slab) and infrared thermal imaging (finds the warm spot precisely).
Repair option A: re-route the failed line through the attic or crawl space, abandoning the slab section. $1,400–$2,800. Future-proofs against the next pinhole on that line.
Repair option B: jackhammer down to the failed section and replace the copper. $1,800–$3,400. Worth it only if you're sure the rest of the slab plumbing is fine.
Full re-pipe of the home (overhead PEX): $8,500–$18,000. The right answer if you've had multiple slab leaks already.