What is a slab leak and how do I know I have one in Atlanta?

How the Signs Show Up

A slab leak is a break in the water or drain piping that runs beneath a poured concrete foundation, often a copper hot water line, sometimes worn through to a pinhole leak. Because the pipe is buried in and under the slab, the signs show up elsewhere first: a water bill that jumps with no new usage, a warm spot on the flooring where a hot line is leaking, low water pressure at a fixture, a hissing sound near the floor, or a cracked tile. Checking your meter reading against a period of no water use is a fast way to confirm it before calling anyone about the under-slab plumbing.

The clearest early sign is a water bill that climbs with no change in how the household uses water. A second sign is a warm spot on the flooring, most noticeable on tile or hardwood, caused by a leaking hot water line warming the slab above it. A hissing sound near the floor when no fixtures are running, low water pressure at the faucets, or a cracked tile that was not there before can all point the same direction.

Why It Happens Under a Slab

Most slab leaks trace back to a pinhole leak in a copper pipe, often from age, water chemistry, or the pipe rubbing against gravel or rebar as the slab settled slightly over the years. Atlanta sits on red clay and saprolite that holds water rather than draining it away quickly, and that soil has real but moderate shrink-swell behavior. As it takes on moisture and expands, then dries and contracts, it can shift a foundation just enough to stress a pipe running beneath it.

This is not unique to any one Atlanta neighborhood. Foundation type here tracks the lot and the era of construction more than the neighborhood name, so a slab-on-grade home near Buford Highway or one in a condo conversion off Chattahoochee Avenue can face the same under-slab plumbing risk as a newer build further out. Once water is escaping continuously under the slab, it does not stop on its own, and the pressure drop at the fixtures tends to get worse rather than better.

What to Do Next

If the water bill has jumped, check the water meter reading with every fixture in the house turned off. If the meter is still moving, water is going somewhere it should not be. Feel the floor in the areas above where main water lines typically run, particularly near a water heater closet or a bathroom wall, for a spot noticeably warmer than the rest of the flooring.

None of these signs confirm a slab leak on their own, but two or more together, a rising bill, a warm spot, low pressure, or a hissing sound, are worth having checked before the water spreads further under the foundation. Atlanta's clay soil already sits close to saturation after a heavy rain, and a slab leak adds to that moisture load from underneath, so catching it early matters more here than the warm spot alone suggests.