Quick answer: A slab leak is a leak in a pipe that runs under or inside your concrete floor. Common signs are a higher water bill, the sound of running water when everything is off, warm spots on the floor and damp flooring. A licensed plumber can find the exact spot without breaking up your whole floor.
Key takeaways
- Slab leaks are hidden, so the signs show up in your bill, floors and walls first.
- Acting early can limit damage to floors, walls and the foundation.
- Plumbers use listening tools, cameras and other methods to pinpoint a leak.
- Repair choices depend on the pipe, where it leaks and how bad it is.
- Do not wait if you see standing water, mold or cracks.
What is a slab leak?
Many homes are built on a concrete slab. Water pipes and drain pipes often run under or inside that slab. Over time, pipes can wear out, rub against concrete, or shift as the ground moves. When a pipe cracks or gets a hole, water leaks into the ground below your home. You cannot see it, and that is what makes it tricky.
What are the warning signs of a slab leak?
- Your water bill goes up and you cannot explain why.
- You hear running water when all taps are off.
- Floors feel warm or hot in one spot, which can point to a hot water line leak.
- Carpet, wood or tile feels damp, lifts or warps.
- You see cracks in floors or walls.
- You notice a musty smell or mold.
- Water pressure drops for no clear reason.
- The water meter keeps moving even when no water is in use.
Any of these signs deserves a closer look. You can read more about our hidden leak and pipe repair work on our residential plumbing page.
How do plumbers find a slab leak?
A good leak detection visit follows a clear path. This is how our plumbers usually work.
Step one: confirm there is a leak
We check your water meter and fixtures to see if water is moving when it should not be. This shows if the leak is real before we go further.
Step two: listen and trace
Special listening tools pick up the sound of water escaping from a pipe. By moving along the floor, the plumber can narrow down where the sound is strongest.
Step three: look inside the pipes
When the leak is in a drain or sewer pipe, a camera inspection shows cracks, breaks or roots from the inside. This is also useful for sewer line leak detection.
Step four: explain the options
After we find the spot, we explain what we found in plain language. You get a clear price before any work starts. You can learn more about how we work on our about us page.
What are your repair options?
| Option | What it means | When it may fit |
| Spot repair | Open the floor in one small area and fix the pipe | One clear leak in a good pipe |
| Reroute | Run a new pipe through walls or the attic and stop using the old one | Pipes under the slab are worn out in many places |
| Repipe | Replace old pipes with new ones | Older homes with aging pipes |
| Pipe lining or patching | Repair the pipe from the inside with little digging | Cracks or leaks in some drain or sewer pipes |
| Traditional excavation | Dig to reach and replace the damaged pipe | Pipes that are too damaged to line or patch |
The right option depends on your pipe type, its age and how bad the damage is. For drain and sewer pipes, trenchless sewer repair can fix problems with less digging. Our CIPP pipe patching and CIPP trenchless pipe lining services are made for this type of repair. If the pipe is beyond saving, our sewer line excavation and replacement team can replace it. For a leaking supply line outside your home, our water line excavation and replacement service can help.
What should you do while you wait for a plumber?
- Turn off the main water valve if you see water spreading.
- Keep rugs and furniture away from wet areas.
- Do not run the dishwasher, washing machine or extra showers.
- Take photos of damp spots, cracks and the water meter.
- Write down when you first noticed the problem.
If water is spreading fast, call us right away at (301) 920-6922 or contact us online for urgent leaks.
What about gas line leaks?
Some homes also have gas pipes under or near the slab. A gas leak is very serious. If you smell rotten eggs, leave your home right away and do not use switches or flames. Call your gas company or emergency services from outside. Then contact our emergency gas services team to check and repair the line safely.
Where do we offer leak detection?
We serve homes and businesses across Maryland, D.C. and Northern Virginia. Check your town on our service areas page, including Laurel, Bowie, Jessup, Germantown and Gaithersburg.
Frequently Asked Questions
How do I know if I have a slab leak?
Look for a higher water bill, the sound of running water, warm floor spots, damp flooring or cracks. You can also check if your water meter moves when all water is off. If you see any of these, book leak detection with our team.
Can a slab leak fix itself?
No. A leaking pipe does not heal on its own, and the damage usually gets worse over time. Call a plumber early. You can see more of our repair work on our services page.
How do plumbers find a leak under a concrete floor?
Plumbers use listening tools to trace the sound of water and cameras to look inside drain lines. This helps them pinpoint the leak without opening a large area. Learn how a camera inspection works.
Do you have to break the whole floor to fix a slab leak?
Not always. Depending on the pipe, the plumber may open only a small area, reroute the pipe, or use trenchless methods for drain lines. See our trenchless sewer repair page to learn more.
Is a slab leak an emergency?
If water is flooding your floor or you smell gas, yes. If the leak is small, it is still best to act soon. Call us through our contact page and we will tell you how fast to move.
Can you find leaks in sewer and gas lines too?
Yes. We can look for sewer line leaks with a camera, and we handle gas line problems safely. Learn more about our emergency gas services.
What causes slab leaks?
Common causes include old pipes, pipe wear from rubbing on concrete, shifting soil and water that eats away at metal. Older homes may have a higher chance. If you are worried about old pipes, ask about our residential plumbing services.