What are the signs of a slab leak?
Short answer
The most common signs are a warm spot on the floor, the sound of running water with all fixtures off, an unexplained rise in the water bill, damp or buckling flooring, a musty smell, and reduced hot-water pressure.
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Confirm it with the meter test
- Turn off every fixture and water-using appliance.
- Note the meter reading or leak indicator position.
- Wait 30 minutes without using water.
- Re-check: any movement means water is escaping the system.
Hot side or cold side?
Closing the cold inlet valve at the water heater isolates the hot lines. If the meter stops moving afterwards, the leak is on the hot side — which is also why hot-water slab leaks often create a warm floor patch.
Related questions
Can a slab leak cause mold?
Yes. Continuous moisture under and around flooring is a common cause of hidden mold growth, especially in humid climates.
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