A slab leak is a leak in a water line that runs under a home's concrete foundation. The pipe sits in or beneath the slab, so the water has nowhere obvious to go, and the leak can run for months before anyone notices it. Plenty of Atlanta-area homes sit on concrete slabs with supply lines underneath.
Caught early, a slab leak is a contained repair. Left alone, it keeps running into the ground under the house and shows up on every water bill until someone finds it.
What a Slab Leak Actually Is
Two kinds of pipe can run under a slab. Water supply lines carry pressurized hot and cold water to your fixtures, and drain lines carry wastewater out. When people say slab leak, they almost always mean a supply line, because a pressurized pipe leaks around the clock whether anyone is using water or not.
That constant flow is what sets a supply leak apart. It turns your water meter overnight. If the leaking line carries hot water, it keeps the water heater cycling and warms the floor above it. A cold-water under-slab leak is quieter. You may not feel a warm spot, but you can still see damp flooring, a climbing bill, or a meter that moves while the house is idle.
A drain line under the slab only leaks when water goes down a drain, so its signs come and go with use. A damp spot or odor after showers or laundry usually points to a broken drain pipe, which is a different job from supply-side leak detection.
Signs of a Slab Leak
Slab leak symptoms show up in three places: the floor, the bill, and the water pressure. Watch for:
- A warm or hot spot on a tile or concrete floor, usually from a leaking hot water line
- Damp carpet, wet spots, or flooring that warps, lifts, or loosens (common with cold-water leaks too)
- The sound of running water when every faucet and appliance is off
- A water bill that climbs while your household's water use has not changed
- A musty smell or mold with no visible source
- Water pressure that drops gradually across the whole house
One of these on its own is not proof. A warm spot plus a water meter that moves while the house is idle is about as clear as a slab leak gets without equipment. That pattern is one of the warning signs Atlanta homeowners notice first before they call for a professional inspection.
How to Check for a Slab Leak at Home
A short meter check tells you whether water is leaving the system. Treat it as a screening step, not a DIY locate-and-fix project.
- Turn off every faucet, appliance, and irrigation zone, including the ice maker and any pool auto-fill.
- Find your water meter, usually in a box near the street, and watch the small leak indicator (a triangle, star, or dial). If it turns while nothing is running, water is going somewhere.
- Close the main shutoff valve where the line enters the house, then watch the meter again.
If the indicator stops once you close the main, the leak is inside the house. If you see no visible drip anywhere, the leak is likely under the slab. If the indicator keeps turning with the main closed, the leak is probably in the service line between the meter and the house, which calls for water line repair rather than slab work.
If your shutoff is stiff or will not close fully, leave it alone and let a plumber run the test. If water is coming up through the floor, close the main if you can and call for emergency plumbing service. Do not cut into flooring or jackhammer concrete to "find" the pipe.
What Causes Slab Leaks
Pipes under a slab stay in contact with concrete, gravel, and soil for the life of the house. Corrosion thins metal pipe until a pinhole opens. Abrasion is the mechanical wear: a hot water line expands and contracts as it heats and cools, and where it touches concrete or rock, that movement rubs a weak spot into the wall. A pipe kinked or nicked when the slab was poured can also fail years later. See our article on how to know if pipes are corroded.
Local ground conditions add stress. North Georgia's clay soil expands when it gets wet and shrinks when it dries. That seasonal movement shifts the ground under slab homes across metro Atlanta and puts pressure on the pipe in or under the concrete. Heavy rain, drought, and winter freeze-thaw swings all add to it. Older homes have had more time for wear to build up, but a newer slab is not immune.
How Plumbers Detect a Slab Leak
Finding a slab leak means finding a spot a few inches wide under a floor you cannot see through. Our technicians use some combination of three methods.
Pressure testing isolates the problem by closing off sections of the system and watching which one loses pressure, so the technician learns whether the leak is on the hot side, the cold side, or a specific branch. Acoustic listening narrows it down. Water escaping a pressurized pipe makes a sound, and listening equipment picks it up through the concrete. Thermal imaging helps with hot water leaks, which show up as a warm pattern on the floor surface.
The point of all three is to mark the leak precisely so only what has to be opened gets opened. Afterward, we go over the results with you, give you a clear report, and walk you through repair options. A hidden break often needs leak detection that finds the leak the first time.
What Happens After the Leak Is Found
The next step depends on where the leak sits, what the pipe is made of, how old it is, and whether this is the first failure or a repeat. In some cases, a small section of floor is opened so that section of pipe can be repaired. In others, the leaking line is abandoned in place, and new pipe is run through the walls or attic so the slab stays intact. When the pipe has already leaked more than once or is in poor shape throughout, replacing a larger part of the system may be the better long-term call.
After detection, we explain your slab leak repair options in plain language and help you choose the path that protects the house. A main water line leak in the yard is a different problem from an under-slab supply leak. If your signs point more to wet spots in the yard than warm floors, start with how to know you have a water line leak.
Frequently Asked Questions
How do I know if I have a slab leak?
Look at the combination of signs, not any single one. A climbing water bill with no change in use, running-water sounds when everything is off, warm spots on the floor, or damp flooring with no obvious source are the usual clues. The meter check above can confirm water is leaving the system. Pinpointing the leak takes professional equipment.
How serious is a slab leak?
It is rarely a flood on day one, but it does not stop on its own. The water keeps running under the house and into the flooring above it, and the meter keeps counting it. Waiting can lead to foundation movement, mold, and damaged flooring.
How long can a slab leak go undetected?
Months, in many cases. Water can soak into the soil below the house before anything reaches the floor, which is why a higher bill or a warm spot is often the first sign.
How common are slab leaks?
Common enough in slab-on-grade homes that every plumber who works in metro Atlanta sees them. Corrosion, abrasion from hot-water expansion, and clay soil movement all add up over time.
How do they fix a slab leak?
A licensed plumber finds the leak first with pressure testing, acoustic listening, and thermal imaging when needed. After that, the repair path depends on the location and condition of the pipe. That might mean opening a small section of floor, rerouting the line so the slab stays closed, or replacing more of the system when failures keep repeating. The right call comes after detection, not before.
Does homeowners insurance cover a slab leak?
It depends on the policy. Some policies treat water damage differently from finding and reaching the pipe, and terms vary by carrier. Ask your agent before repairs start, and keep the leak detection report.
Finding the Leak Under Your Floor
Start with the meter. If water is moving while the house is idle and you cannot find a drip anywhere, call Dalmatian Plumbing or contact us online for slab leak repair. We will schedule leak detection, find where the water is going, and clearly explain what it will take to stop it.
