Slab Leak

A slab leak occurs when copper, PEX, galvanized, or cast-iron piping embedded in or under a concrete slab ruptures, corrodes through, or develops a pinhole. Supply lines are the concern in most cases—they're pressurized and waste water fast. Drain lines can leak too but usually announce themselves with odor or wet spots rather than surprise water bills.

Detection matters because the leak is invisible. Look for hot spots in flooring (hot water lines), cracks radiating across the slab, mold or efflorescence around baseboards, soft spots in concrete, or unusually high water consumption with no obvious source. A moisture meter and thermal imaging help. Acoustic listening devices or dye tracing can pinpoint the exact location, though sometimes you just follow the wet spot.

Repair options depend on code, line type, and access. You can reroute the line above-slab through walls or attic—this kills the problem permanently but takes time and skill. Epoxy pipe coating sometimes works on old corroded lines if the hole is tiny and you're confident in the material. Trenchless repair exists but isn't standard in residential work. If the slab is old galvanized or failing cast-iron, strongly advise the customer that one leak often means more are coming; they're buying time, not a fix.