Slab Leak Signs: What to Watch For and How to Check

Is your house on a slab at all?

A slab leak can only happen where water lines run under or inside a concrete floor poured on the ground. Metro Atlanta has every kind of foundation. Older houses, including the early-1900s bungalows in neighborhoods like Virginia-Highland, are often built over crawl spaces or basements, where a leaking pipe can be seen and reached from underneath. Slab construction is more common in newer subdivisions, townhomes, garages and additions. The suburbs skew newer: Census survey data puts the median year built at 1998 in Kennesaw, where only about 11 percent of homes are older than 1980. Some houses are a mix, with a crawl space under the original rooms and a slab under a later den or garage. If you can open a crawl space door and see floor joists, look there first.

Some local building departments treat under-slab piping as its own inspection stage. Duluth's inspection list includes a slab plumbing inspection, and Woodstock schedules under-slab plumbing inspections under the plumbing permit, which tells you how many new homes in the area are built with water lines in the concrete.

What are the warning signs?

No single clue proves a slab leak. A pattern of several does, and each one has a more ordinary explanation you should rule out first.

Fixr's 2025 slab leak guide lists most of these, along with a raised or domed floor and hot or cold spots underfoot. A water heater that seems to run constantly fits the pattern when the leak is on the hot side. Before suspecting the slab, put a few drops of food coloring in each toilet tank and wait without flushing. Color in the bowl means a worn flapper, which is a far more common cause of a high bill and a simple toilet repair.

How can you check for a leak at home?

EPA's WaterSense program gives the basic test: read the water meter, use no water for two hours, then read it again. If the meter changes at all, you probably have a leak. To narrow it down:

1. Shut off the ice maker and irrigation, and make sure nobody uses water during the test.
2. Find the meter box near the street and note the reading. Many meters also have a small leak indicator that turns at very low flow.
3. If the meter is moving, close the main shutoff at the house and watch again.
4. Meter stopped: the leak is inside the house, in a wall or under the slab. Meter still moving: suspect the buried line between the meter and the house.
5. At night, with the house quiet, walk the floors and listen near the water heater, and feel tile barefoot for a warm strip.

Putting it in perspective, EPA estimates the average household's leaks waste more than 9,300 gallons a year, and about 9 percent of homes have leaks losing 50 gallons or more a day. Most of that comes from toilets, faucets and fixtures, not slabs, which is why the simple checks come first.

Why do slab pipes fail around Atlanta?

Fixr lists four main causes: expansive soils that swell and shrink, pressure from soil movement that can crack pipe, corrosion-prone pipe materials such as galvanized steel, cast iron and copper, and aggressive water chemistry, especially acidic water. Abrasion where a pipe rubs against concrete or gravel and poor original workmanship add to the list. A slab on expansive soil that has been soaked by a leak, or dried out and wetted again, is under more stress than one on stable ground, and hot water lines tend to give out first.

How do plumbers find the exact spot?

The aim of professional detection is a mark on the floor precise enough that only a small patch of concrete, if any, has to come up. A visit usually combines a few methods: isolating the hot side from the cold side at the water heater, pressure-testing sealed sections to see which one drops, listening through the floor with acoustic gear, scanning with an infrared camera for a warm streak, and tracing the pipe's route with a locator. HomeAdvisor's June 2026 figures put detection at $150 to $400; Fixr's 2025 range is $100 to $400. Ask for electronic leak detection before anyone starts cutting concrete.

What does a repair cost?

Across all methods, HomeAdvisor puts the average at $2,280 with a typical range of $630 to $4,400. Fixr's average is $2,500, with most jobs between $1,000 and $4,000. The reroute numbers differ widely because one short hot water line through an open wall and every buried line in a large house are very different jobs. Flooring, drying and drywall are usually separate bills from other trades.

The condition of the pipe drives the choice. One leak in otherwise sound pipe is a good case for a spot repair under the slab. A second or third leak on the same buried line suggests more are coming, and a reroute or a full supply repipe ends the cycle. In the City of Atlanta, replacement plumbing in one- and two-family homes is permitted online through the Office of Buildings, and the plumber normally pulls it.

How urgent is it, and who pays?

Water seeping between tiles, flooring that has started to buckle or a meter dial spinning fast all mean you should close the main now and follow the first-ten-minutes checklist. A slow leak with none of those signs can be booked as a normal appointment, but it keeps wetting the soil under the foundation every day it runs.

If the meter test pointed to the yard, the problem is on the service line. Atlanta Watershed Management, Cobb County, DeKalb County, Gwinnett County, Fulton County and the Clayton County Water Authority all make the owner responsible for the line from the meter to the house, so a yard line leak repair is normally a private job. Insurance varies: some policies pay to reach the pipe, others only for resulting water damage, and few cover the worn pipe itself, so call your agent before the floor is opened. Local plumbers who handle slab work are available through this service across the metro, including a Kennesaw slab leak and homes in Duluth. The full guide library covers related problems.