Slab Leak Guide
Leak Finder · 3 questions · under a minute

Something is leaking.
Let's find where.

A water bill that jumped, a warm spot on a tile floor, a puddle under the water heater, a drain that gurgles. Narrow down the likely source before anyone breaks concrete.

Open the Leak Finder Typical repair costs
Cutaway of a house on a concrete slab with a small glowing leak in a pipe under the floor, a water heater in the garage and a sewer pipe under the yard
Leaks can start where you can't see them: under the slab, at the water heater, or in the sewer line.

What are you noticing?

Warm or damp spot on the floor One of the signs of a leak under a slab. Water bill jumped Nothing visible, but the meter tells the story. Puddle by the water heater Top, relief valve, or the tank itself? Stain on a wall or ceiling Supply line, drain, or a fixture seal. Soggy patch in the yard Could be the buried water line. Gurgling drains or sewer smell One fixture, or the main line?

Slab leak repair, in numbers

$2,300average slab leak repair (This Old House)
$630–$4,400typical range — or more
$150–$600professional leak detection

Source: This Old House, Slab Leak Repair Cost (updated Apr 7, 2026; HomeAdvisor data). The full breakdown is in the Leak Finder.

Leak library

Does Homeowners Insurance Cover Sewer Lines?How Long Do Water Heaters Last? (+repair vs replace)How to Find a Water Leak UndergroundIs a Slab Leak Covered by Insurance?No Hot Water? What to Check FirstRepair or Replace a Water Heater: CalculatorSewer Camera Inspection Cost (2026)Sewer Line Repair Cost (2026)Slab Leak Detection Cost (2026)Slab Leak Repair Cost: Reroute vs Epoxy Lining vs Direct Access (2026)Slab Leak: Signs, Causes, What to DoTree Roots in Sewer Line: Signs, Causes and FixesTrenchless Sewer Repair Cost: Lining vs Pipe BurstingWater Heater Leaking From the Bottom: What It MeansWater Heater Leaking From the Top: Causes and FixesWater Heater Pressure Relief Valve Leaking: Causes and FixesWhat Causes a Slab Leak?

Illustrations on this page are AI-generated to help you picture the situation. They are not photos of real homes, jobs or people.

When to call a licensed plumber

Water spreading across a floor, a warm spot on a slab floor, a leaking water heater, or sewage backing up into a drain needs a licensed plumber. Keep away from water near outlets or appliances, and shut off the water at the main valve only if you can reach it safely. If you smell gas near a gas water heater, leave the house and call your gas utility or 911 from outside. Never plug or cap a water heater's relief valve. Before anyone digs in your yard, call 811.