Signs of a Slab Leak in an Arizona Home

The warm spot

Walk the house in socks. A hot line under the slab warms the concrete above it, and tile and stone carry that heat right up to your feet. It's usually a patch a foot or two across, in a hallway or near a bathroom, and it stays warm whether or not anyone's been running hot water. Pets find it first. If the dog has a new favorite spot on the tile, go stand there.

Cold line leaks don't give you this, which is why the other signs matter.

The other signs

Your water bill went up and nothing about the house changed. That's often the first sign of a cold line leak, months before anything shows.

You can hear water running when nothing is on. Stand in the quietest room at night and listen near the floor.

Hot water takes longer to arrive, or runs out sooner. A hot line leak is dumping heated water into the dirt, so the heater works harder and you get less.

Flooring is doing something. Grout darkening in one area, laminate lifting at a seam, carpet that's damp at the tack strip, a wood floor cupping. Water under a slab comes up through the concrete slowly, and the floor finish shows it before the concrete does.

A musty smell you can't trace. Mildew under flooring is a slab leak smell.

Low pressure at one fixture or across the house, especially if it came on gradually.

Cracks in tile or drywall that weren't there last year. Soil under a slab that stays wet can move, and the house tells you.

The ten minute test

Turn off every fixture in the house. The ice maker, the RO system, the irrigation controller, the pool autofill, all of it. Then go out to the meter box near the sidewalk and lift the lid. Most meters have a small leak indicator, a little triangle or star, that spins when any water is moving. Watch it for ten minutes. If it moves, or the last digit on the register moves, water is leaving the house somewhere. Everything past the meter is yours. Chandler's water FAQ spells it out: plumbing after the city's meter is the homeowner's responsibility.

A moving meter doesn't tell you where. It could be the yard line between the meter and the house, a toilet flapper, or the slab. But a moving meter plus a warm spot, or a moving meter plus a floor doing something, is a slab leak in our experience.

Why it happens here

Most East Valley homes sit on a slab with no crawlspace, and many of those slabs are post-tensioned, with steel cables under tension running through the concrete. Gilbert publishes its own certification form for post-tension foundations on one and two family homes. That's why nobody should cut into a slab on a guess. Detection first, one hole, in the right place.

Then there's the water. Chandler averages 16.5 grains per gallon. Mesa runs 12 to 22 depending on the plant. Copper that's carried that water for 25 or 30 years is due. Hot lines take the most wear because they expand and contract with every shower, and where the pipe rubs on concrete or rebar it wears thin.

What happens when you call

We do electronic leak detection first: listening equipment, thermal imaging on a hot line, pressure tests on isolated sections. It ends with a mark on the floor and a written price for the fix. The fix is one of three things: open the slab at that spot and repair the section, reroute that line through the attic and abandon the one under the slab, or repipe if this is the third leak in the same aging copper. What those ran on our invoices is on the cost guide linked below.