Short answer
A slab leak often shows up first as a higher-than-normal water bill, a warm or damp spot on an otherwise cool tile or concrete floor, or the sound of running water when every fixture in the house is off. Cracked or lifting flooring and a persistent musty smell are later signs. Because the leak is under the concrete, do not try to locate or dig it out yourself, have it inspected.
Why Las Vegas Homes Are Prone to Slab Leaks
Most homes in the Las Vegas valley are built slab-on-grade, meaning the concrete foundation sits directly on the ground with no basement or crawl space underneath. Water and, in many homes, copper or PEX supply lines run through or under that slab, which means a leak in those lines is hidden by concrete, flooring and sometimes a slab that has shifted slightly over the years.
Because you cannot see the pipe, a slab leak is usually identified by its side effects rather than by spotting the leak itself. Knowing what those side effects look like is the difference between catching it early and finding out only after flooring and drywall have already been damaged.
Age plays a role too. Across Clark County, more than half of housing units were built before 2000, with a median year built around 1997, so a large share of local homes now have plumbing that has been buried under the slab for decades. Older copper lines can develop pinhole leaks from corrosion over time, and even newer PEX lines can be damaged at a fitting or where the slab has shifted slightly.
Your Water Bill Goes Up for No Reason
If your household habits have not changed but your water bill climbs noticeably from one billing cycle to the next, that is one of the more reliable early indicators of a hidden leak somewhere in the system, including under the slab. A slab leak can run continuously, even in small amounts, for weeks before it becomes visible in the house.
A simple check is to make sure every faucet and appliance in the house is off, then look at your water meter. If the meter's leak indicator is still spinning or the dial is still moving with everything off, water is going somewhere it should not be.
A Warm Spot or Damp Area on the Floor
If the leak is on the hot water line, you may notice one area of tile, vinyl or even carpet that feels noticeably warmer than the rest of the floor, sometimes years before any visible damage shows up. A leak on the cold line is harder to notice this way but can still leave a persistently damp or cool patch.
You might also hear the sound of water running or hissing under the floor in a quiet room, especially when the house is otherwise silent, even though every fixture is off.
Flooring and Baseboard Changes
Over time, water escaping under the slab can work its way up through grout lines or the edge of the flooring, leading to cracked tile, lifting vinyl, warped wood flooring, or baseboards that feel damp or have started to separate from the wall. In some cases, you may notice a hairline crack in the slab itself, visible where flooring has been removed or at an exposed edge.
- Tile that sounds hollow or cracks without an obvious cause
- Baseboards or flooring near an exterior wall that feel damp
- A section of carpet that stays damp or smells musty
- Warped or buckling wood or laminate flooring in one area
Musty Smell or Rising Humidity
A slab leak that has been running for a while often produces a persistent musty or earthy smell in the affected room, even without any visible water. This happens because moisture is reaching materials like carpet padding, drywall, or the underside of cabinetry, conditions where mold can begin to grow within 24 to 48 hours of sustained moisture.
If a room consistently feels more humid than the rest of the house, or a smell keeps returning no matter how often you clean, that is worth having checked rather than masked with air freshener.
Unexplained Low Water Pressure
A significant leak under the slab can reduce water pressure at one or more fixtures in the house, since some of the water is escaping into the ground before it reaches the faucet. If pressure has dropped noticeably at a specific sink or shower, and not the whole house, that can point toward a leak somewhere along the line feeding that fixture.
This sign is easy to dismiss on its own, since Las Vegas' hard water can also reduce pressure over time by narrowing pipes and fixtures with mineral buildup. If low pressure shows up suddenly rather than gradually, or appears alongside any of the other signs above, treat it as a reason to have the system checked rather than something to wait out.
What to Do If You Suspect a Slab Leak
Do not attempt to locate or dig up a suspected slab leak yourself. Finding the exact point of a leak under concrete takes specialized equipment, including acoustic listening devices and thermal imaging, and cutting into the wrong spot in the slab can create more damage without solving the problem.
For a free inspection, our number is (702) 213-9556, staffed any hour of the day, in English or Spanish, and we can check moisture patterns, help confirm whether a slab leak is likely, and explain what repair and drying options look like for your specific home.
Waiting rarely helps with a slab leak, since the water does not stop moving on its own and the longer it runs, the more of the flooring and framing above it tends to absorb moisture. Getting an inspection scheduled once you notice a warning sign is the most useful next step, even if the signs still seem minor.
