Signs of a slab leak include warm spots on the floor, the sound of running water with everything off, a water meter that keeps moving, and a sudden jump in your water bill. Confirm it with a meter test, then close the water heater inlet to see whether it's a hot or cold line. Finding the exact spot under concrete takes professional acoustic, thermal or tracer gas equipment.
A slab leak is a leak in a water line that runs under your home’s concrete foundation. Many homes in Bargersville and newer Johnson County subdivisions are built on slabs, with copper or PEX supply lines running beneath the concrete. When one of those lines leaks, the water goes into the soil, not onto your floor, so the signs are subtle at first.
Signs of a slab leak
- Warm spots on the floor. Walking barefoot on tile and finding one spot warmer than the rest is a classic sign of a hot water slab leak.
- Sound of running water when every faucet and appliance is off.
- The water meter keeps moving with no water in use.
- A jump in the water bill with no change in how you use water.
- Damp or discolored flooring, or carpet that feels wet with no spill.
- New cracks in tile or the slab, or baseboards that swell.
- Water heater running constantly, if the leak is on the hot side.
- Low water pressure throughout the house.
One sign alone can have other causes. Two or three together are a strong reason to test.
Step 1: Confirm there’s a leak
Do the meter test:
- Turn off every faucet, fixture and appliance, including the irrigation.
- Note the meter reading and the leak indicator.
- Wait one to two hours without using water.
- If the meter moved, water is escaping.
Then rule out the easy sources: toilets, faucets, the water heater, the softener. Our guide on how to find a water leak in your house walks through each one.
Step 2: Is the leak inside or outside?
Close the main shutoff valve where the water enters the house and watch the meter.
- Meter stops: the leak is inside the house, a slab leak is possible.
- Meter keeps moving: the leak is in the service line outside. See how to find an underground water leak.
Step 3: Hot side or cold side?
Open the main shutoff again and close the cold water inlet valve on top of the water heater.
- Meter stops: the leak is on the hot water side. Warm floors usually confirm it.
- Meter keeps moving: the leak is on the cold water side.
If it’s a hot water leak: leave the water heater inlet closed until the repair to stop the leak and save energy. Turn a gas water heater to “vacation” or a pilot setting, or switch off power to an electric heater, while it has no water coming in.
Step 4: Pinpoint the exact spot
This is where DIY ends. Concrete, tile and flooring hide the pipe, and guessing is expensive: every wrong opening means more concrete and flooring to replace.
Professional slab leak detection combines:
| Method | What it does |
|---|---|
| Pressure testing | Confirms which line is leaking |
| Acoustic ground microphones | Listen through the slab for the hiss of water escaping. The loudest point marks the leak. |
| Thermal imaging | Shows the warm bloom of a hot water leak on the floor surface |
| Line tracing | Maps where the pipe actually runs under the slab |
| Tracer gas | Finds quiet leaks in PEX or small leaks that are hard to hear |
The leak is marked on the floor so your plumber opens one small area. Read more about how professional leak detection works.
What causes slab leaks?
- Abrasion: pipes rubbing against concrete, gravel or each other as the house settles and the pipes expand and contract
- Water chemistry and age: pinholes in older copper lines
- Soil movement: shifting or expanding soil putting stress on lines
- Installation issues: kinks, poor joints or damage during construction
What happens after the leak is found
The common repairs are a spot repair at the marked spot, a reroute that bypasses the leaking section through walls or the attic, or a repipe if the lines are old. See what slab leak repair involves and costs.
Get your slab leak located
If your tests point to a slab leak in Bargersville or elsewhere in Johnson County, our slab leak detection service finds and marks it without breaking the floor to search.
Still can’t find it?
Our slab leak detection pinpoints the leak without tearing things up, so the repair starts in the right spot.
Frequently asked questions
What are the first signs of a slab leak?
Warm or damp spots on the floor, the sound of running water when nothing is on, a water meter that keeps moving, and a water bill that jumps with no change in use. Cracks in flooring and swelling baseboards can follow.
Can I find a slab leak myself?
You can confirm that a slab leak is likely with a meter test and hot/cold isolation. Pinpointing the exact spot under concrete requires professional equipment such as acoustic ground microphones, thermal imaging or tracer gas.
Is a hot water slab leak an emergency?
It should be handled quickly. A hot water slab leak wastes water and energy, can damage flooring and may affect the soil under the foundation. Closing the cold water inlet to the water heater stops the flow until the repair.
How is a slab leak repaired after it's found?
The usual options are a spot repair through a small opening in the slab, rerouting the line through walls or the attic, or repiping. The right choice depends on the pipe's age and condition.