What Are the Signs of a Slab Leak Under My House?
Last updated October 25, 2026
The short answer
Listen for Running Water
One of the clearest signs of a slab leak is the sound of water moving under your floor. Turn off all faucets and appliances, then stand still in a quiet room. If you hear a hissing or trickling noise, water may be escaping from a pipe beneath the concrete.
The sound can be faint, especially if the leak is small. Walk around the house and listen near interior walls and floor edges. A persistent sound, even when everything is off, points to a hidden leak. If you notice this, shut off your main water valve and call a plumber or a leak detection service.
Check Floor Temperature and Moisture
A slab leak can warm or dampen your floor. Place your hand on the concrete in different rooms. A warm spot, especially in a cool season, may indicate hot water leaking from a pipe. Likewise, a cold, wet patch can signal a cold water line issue.
Moisture can also seep up through carpet, tile, or hardwood. Look for discolored grout, bubbling paint, or a musty odor. If you find dampness, dry the area and watch for mold. Mold can spread quickly, so address any water intrusion promptly.
- Warm or cold spots on the floor
- Damp carpet or wet tiles
- Musty or earthy smell
- Cracks in the slab or grout
- Rising water bill with no usage change
- Drop in water pressure when using fixtures
Watch Your Water Bill and Pressure
A sudden spike in your water bill, with no change in household use, is a strong clue. Slab leaks can waste gallons of water daily. Compare your current bill to the same month last year. If the increase is large and unexplained, a hidden leak is likely.
Water pressure can also drop when a leak diverts flow. If faucets or showers run weaker than usual, especially after a period of no use, investigate. Turn off all water and check your meter. If it still moves, you have a leak. Act quickly to minimize damage.
Inspect for Structural Cracks
Water eroding soil under the slab can cause the foundation to settle. Look for new cracks in interior walls, ceilings, or the slab itself. Small hairline cracks may be normal, but widening gaps or uneven floors suggest movement. These signs often accompany a slab leak.
If you see cracks, do not ignore them. They can worsen over time and lead to costly structural repairs. A water damage inspection can help determine the extent. The pros use moisture meters and other tools to map the leak and assess the impact on your home.
What to Do Next
If you suspect a slab leak, shut off your main water valve right away. This stops further water damage and reduces your water bill. Then call a plumber to locate the exact pipe break. A leak detection service can find the leak without tearing up your whole slab.
After the leak is fixed, you may need to dry out the area and repair any damaged drywall or flooring. If water has spread, consider structural drying and dehumidification to prevent mold. If you live in Layton, keep your shutoff valve location written down. The pros can handle the cleanup, but you must act first.
Need help right now?
Phones are answered 24/7 for Layton and nearby communities.
Call Now (801) 383-0232Frequently asked questions
How do I know if the sound is a slab leak or something else?
Turn off all water and listen. If the sound stops, it was normal flow. If it continues, it is likely a leak. You can also check your water meter for movement when everything is off. A professional leak detection service can confirm with specialized equipment.
Can a slab leak cause mold in my house?
Yes. Moisture from a slab leak can seep through the slab and into drywall, carpet, or wood framing. Mold can grow within 24 to 48 hours. Look for dark spots, musty smells, or allergic reactions. If you see mold, contact a mold professional for safe removal.
Will my insurance cover slab leak damage?
Policies vary, and your insurer decides what is covered. Some policies cover sudden water damage, while others exclude gradual leaks. Review your policy and contact your insurance company. Document the damage with photos and keep records of any repairs. Check your policy for specific exclusions.