Slab leak: the $100-a-month leak hiding under your floor
Slab leaks are the water damage that announces itself late — here's how to catch it early and what each repair method honestly costs.
You're reading this because your water bill keeps climbing, there's a warm spot on the kitchen floor, and nobody can find a visible leak anywhere.
Those three facts together are the textbook slab-leak signature. Catching it now vs. in a year is the difference between a $1,500 reroute and a $15,000 excavation — and this page tells you which repair method fits your situation before any plumber pitches one.
Ranges below come from published national data across the three standard repair methods. We mark verified quotes when we have them; the matching service below gets you 2–3 real bids.
Those three facts together are the textbook slab-leak signature. Catching it now vs. in a year is the difference between a $1,500 reroute and a $15,000 excavation — and this page tells you which repair method fits your situation before any plumber pitches one.
Ranges below come from published national data across the three standard repair methods. We mark verified quotes when we have them; the matching service below gets you 2–3 real bids.
The telltale signs (check them in 5 minutes)
- Water bill spike with no behavior change — check the meter: with everything off, if the flow indicator moves, you have a leak somewhere.
- Warm floor spots (hot line) or unusual cold spots; tile that sounds hollow when you knock.
- Sound of running water when every fixture is off — put your ear to the floor near the suspect zone.
- New hairline cracks in slab/flooring, or a musty smell with no visible water.
- Neighbors' history: galvanized or polybutylene pipe houses (1960s–1990s) in your tract leak at statistically similar rates.
The three repair methods — and their real prices
| Method | Typical cost | When it's the right call |
|---|---|---|
| Spot repair (tunnel/jack one point) | $1,500 – $4,000 | Single confirmed leak point, accessible path |
| Pipe bursting (replace line under floor) | $3,000 – $8,000 | Multiple leaks / aged galvanized whole line |
| Reroute above slab (abandon old line) | $1,500 – $5,000 | Often the smartest value: new PEX through walls/attic, old line dead |
| Full excavation & repipe | $8,000 – $15,000+ | Slab damage, failed previous repairs |
| + Water mitigation if slab was saturated | + $1,000 – $5,000 | Drying clock starts at discovery — see cost hub |
Detection itself ($150–$500 for electronic/thermal leak location) is usually billed separately and often waived if you book the repair — always ask. Sources →
Ask every plumber these three questions
- "Will you do electronic/thermal detection before opening any floor?" (No = walk.)
- "What's the lifetime expectation of THIS repair vs. a reroute?" (A pitch for only one method is a red flag.)
- "Does your quote include drying/moisture logs, or separate?" (Surprise line items live here.)
Two plumbers, one answer
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