Slab Leak Signs: What a Leak Under Your Floor Looks Like

A leak under concrete is easy to miss. The water has somewhere to go, into the soil and the slab, so it can run for weeks before anything shows on the surface. By then it may have soaked carpet pad, swelled wood flooring and wicked into the bottom of walls. The plumbing repair is a job for a plumber. If the water has already damaged floors or walls, ReestorianPros can connect you with a local provider for water mitigation and structural drying in Littleton.

This is general information. A plumber with leak-detection equipment is the one who confirms where a slab leak is.

What is a slab leak?

"Slab leak" describes any leak in a pipe that's buried in or under a concrete floor. That includes hot and cold supply lines, which are under pressure and leak all the time, and drain lines, which leak only when water runs down them. In the Denver area, slab leaks can happen under a basement floor, a garage, a slab-on-grade addition or a house built without a basement.

How do I know if I have a slab leak?

Look for more than one of these signs together:

• The water meter moves when every faucet and appliance is off
• Warm spots on the floor, especially on tile or concrete, from a leaking hot water line
• Damp or wet flooring, carpet that never fully dries or vinyl that feels soft
• Hardwood or laminate that cups, swells or lifts at the seams
• New cracks in tile, concrete or drywall near the floor
• A musty smell that's strongest near the floor
• The sound of running water when nothing is on
• A higher water bill with no change in how you use water
• Low water pressure at fixtures across the house
• A water heater that runs more than usual

What to do right now if you suspect a slab leak

1. Look for water coming through the floor. If you see it, close the main water shutoff.
2. Run the meter test below to confirm a leak.
3. Move rugs, furniture and boxes off damp flooring.
4. Photograph the floor, walls and meter before anything is opened.
5. Call a plumber with leak-detection equipment to find the pipe.
6. Call a water damage provider if flooring, carpet or walls are wet.
7. Tell your insurer if the damage is more than a small spot.

How to check for a slab leak with your water meter

Denver Water describes a simple test that works for any hidden leak:

• Turn off every faucet, fixture and water-using appliance.
• Note the meter, including the small red triangle or gear-shaped leak indicator.
• Wait at least 30 minutes without using water, then check again.
• If it moved, close the main shutoff valve. If the meter stops, the leak is inside the house, which includes under the slab. If it keeps moving, the leak is underground between the meter and the shutoff.

Denver Water says property owners are responsible for the service line from the main into the home, while the utility handles its meters and mains.

To narrow it down further, many homes have separate shutoffs for the water heater. If the meter stops moving when you close the cold-water valve to the heater, the leak is likely on the hot side.

What causes a slab leak?

• Corrosion of older copper or galvanized pipe from the outside in, or from water chemistry inside
• Abrasion, where a pipe rubs against concrete, gravel or another pipe as it expands and contracts
• Ground movement, which bends or pulls pipes
• Poor installation, such as kinked pipe or weak joints
• High water pressure, which strains joints and fittings over time

Do Colorado's swelling soils cause slab leaks?

The Colorado Geological Survey calls swelling soil a common and sometimes serious problem in Colorado. It says that all major population centers on the eastern slope sit partly on soils that can swell, and that floor slabs and flatwork are the parts of a house most affected. Its homeowner guide lists sprinkler system and water main leaks among the ways soil gets wet, and it advises checking water, sewer and gas pipes for bowing or pulling apart. In other words, a leak can wet the soil, the soil can move the slab, and a moving slab can stress the pipes in it.

Is it a slab leak or something else?

Not every damp floor is a slab leak. Rule out these first:

If the meter doesn't move with everything off, a supply-side slab leak is unlikely. A drain leak is still possible, so watch whether the damp area grows after showers or laundry. For a wet wall instead, read how to find a water leak in a wall.

How do plumbers find a slab leak?

These tools let a plumber open only a small section of floor, if any, instead of guessing.

How to fix a slab leak

A plumber can explain which option fits your pipes and your floor. In Littleton city limits, contractors need a current city license, and the city requires permits to repair or replace plumbing systems, so ask about permits when you get a quote.

Water damage from a slab leak

Repairing the pipe stops new water. It doesn't dry what's already wet. Water from a slab leak usually spreads sideways under flooring and wicks up into baseboards and the bottom of drywall. A drying job typically includes:

1. Moisture mapping across the floor and nearby walls to see how far the water went
2. Removing flooring, pad or baseboards that can't be dried in place
3. Drying the slab and walls with air movers and dehumidifiers
4. Taking daily moisture readings until materials reach a dry standard
5. Photos and readings for your insurance claim

Concrete holds water and releases it slowly, so drying should be checked with a meter, not by touch. The EPA says mold usually won't grow if wet materials are dried within 24 to 48 hours. A slab leak has often been running much longer than that, so check for mold too. See signs of hidden water damage for more on finding the wet areas.

Is a slab leak covered by insurance?

Coverage depends on your policy and how the damage happened. Many policies cover sudden water damage but exclude slow leaks, wear and tear, and poor maintenance. Some pay to access the pipe and repair the resulting damage but not the pipe itself. Photograph the damage, keep the plumber's report on the cause, report the loss promptly and read does homeowners insurance cover water damage in Colorado?

How much does slab leak repair cost?

ReestorianPros doesn't set or publish prices. The cost of a slab leak depends on how hard the leak is to find, which repair method fits, how much concrete and flooring has to be opened, and how much water damage needs drying and rebuilding. Ask for a written estimate that separates the plumbing repair from the water damage work.

How to prevent slab leaks

• Know your water pressure. Ask a plumber to check it and whether a pressure-reducing valve makes sense.
• Watch the meter. Run the meter test once or twice a year.
• Keep water away from the foundation. The Colorado Geological Survey advises keeping sprinkler spray at least 5 feet from the foundation and discharging downspouts at least 5 feet away.
• Fix leaks fast, including irrigation and outdoor faucet leaks near the house.
• Plan ahead in older homes with original pipes, especially after one leak.

Related reading: If the floor is wet near the water heater, see water heater leaking: what to do right now. To check for other hidden damage, read signs of hidden water damage.

When should you call a water damage professional?

Call a professional when:

• Flooring is wet, lifting or soft over a large area
• Water has wicked into baseboards or the bottom of drywall
• The leak ran for days or weeks before it was found
• You smell mustiness near the floor after the pipe is repaired
• You need moisture readings and photos for an insurance claim

Slab leak in Littleton? Call (303) 879-0950 to reach a local water damage provider.