What Are the Signs of a Slab Leak Under My House?
Last updated October 25, 2026
The short answer
Listen for Water Sounds
A slab leak often makes a hissing or rushing water sound that you can hear even when all faucets and appliances are off. Stand still in quiet rooms, especially near interior walls or the floor, and listen carefully. The sound may be faint, so turn off the TV and any fans to hear it better.
If you hear water running but cannot find a source, that is a strong signal. Check your water meter to see if it moves when nothing is using water. A moving meter confirms a leak somewhere, and a slab leak is a likely suspect if the sound seems to come from under the concrete.
- Hissing or rushing noise under the floor
- Water meter moves with all fixtures off
- Sound is louder near the slab perimeter
- No visible water source matches the noise
Check for Warm Spots
Hot water lines running through the slab can create warm patches on your floor when they leak. Walk barefoot across the concrete or tile, especially in hallways or rooms where pipes run. A warm area that persists is a classic sign of a hot water slab leak.
Warm spots may also come with a slight dampness or a faint odor. Do not ignore them, as the leak can worsen and cause more damage over time. If you find such a spot, note its location and move on to checking other signs.
- Unexplained warm areas on the floor
- Warmth persists even after the heat is off
- Dampness or musty smell accompanies the warmth
- Spot is in a consistent location over time
Watch Your Water Bill
A sudden, unexplained increase in your water bill is one of the most reliable indicators of a hidden leak. If your usage habits have not changed, but the bill jumps, a slab leak could be the culprit. Compare bills from the last few months to spot the trend.
Keep in mind that outdoor watering or a running toilet can also raise the bill. Rule those out first by checking your irrigation system and toilet flappers. If the increase remains a mystery, a leak under the slab becomes more likely. Policies vary, and your insurer decides what is covered.
Look for Cracks and Damage
Water escaping from a slab leak can undermine the soil beneath your foundation, causing it to shift. This often results in new cracks in drywall, tiles, or the slab itself. You might also notice doors or windows that stick, or floors that feel uneven.
Cracks alone do not always mean a leak, but combined with other signs, they point to trouble. Pay attention to cracks that appear suddenly or grow wider. Also check for buckling or warping in hardwood or laminate flooring, which can happen when moisture rises from below.
Test Water Pressure
A slab leak can reduce water pressure throughout your home because water escapes before reaching fixtures. If your shower or faucets seem weaker than before, and you have ruled out clogged aerators, a leak may be the cause. Low pressure often appears alongside other signs like sounds or warm spots.
You can do a simple test by turning on all cold water taps at once and listening for changes. If the pressure drops noticeably, note it. This information helps the pros pinpoint the problem. For thorough detection, consider a leak detection service and water damage inspection.
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Call Now (469) 698-4610Frequently asked questions
Can a slab leak cause foundation problems?
Yes, water washing away soil under the slab can lead to settling or shifting. This may cause cracks in walls, floors, or the foundation itself. Early detection and repair help limit structural issues, but the extent of damage varies.
How do pros find a slab leak?
Pros use methods like acoustic listening devices, infrared cameras, and pressure testing to locate the leak without tearing up your floor. These tools help pinpoint the exact spot, so repairs are targeted and less invasive.
Should I turn off my water if I suspect a leak?
Yes, turning off the main shutoff valve can stop the flow and prevent further damage. Find your shutoff valve now, before an emergency. If you live in Rockwall, keep its location written down for quick access.