9 Signs You Have a Slab Leak

A slab leak hides under concrete, so it rarely announces itself with a visible puddle. Instead it leaves clues — a bill that jumps, a floor that feels warm in one spot, a sound you cannot explain. Any one of these signs can have another cause, but two or more together are a strong reason to test. This checklist covers the nine most reliable signs Olathe homeowners should watch for, and it ends with a free meter test you can do in 15 to 20 minutes. If you are seeing several of these, our slab leak detection and repair in Olathe team can confirm whether you have a leak and where it is.

The 9 Signs

1. Your Water Bill Spikes

This is the most common first sign. Compare the same months in prior years, not just last month — a leak can push usage up by hundreds or thousands of gallons, and the bill is often the first place it shows. If your usage jumped and nothing in your household changed, a hidden leak is the first thing to rule out. See our guide to high water bills for the other causes to check.

2. Warm Spots on the Floor

A hot-water line leak warms the slab above it. Walk barefoot across the floor, especially in the morning, and feel for a patch that is noticeably warmer than the floor around it. A warm spot that stays in the same place day after day is a strong clue — sunlight and heating vents move, a leak does not.

3. The Sound of Running Water

Stand quietly in the house with every tap, toilet and appliance off. If you can hear water running, hissing or trickling — often near a wall or through the floor — water is moving somewhere it should not be. This is one of the more reliable signs, because a healthy plumbing system is silent when nothing is running.

4. Low Water Pressure

A leak lets pressure escape before the water reaches your fixtures, so showers and taps can feel weaker than usual. Low pressure has other causes too, such as a failing pressure regulator or a partially closed valve, but if it appears alongside a high bill or a warm floor, a leak moves to the top of the list.

5. Damp or Warped Flooring

Moisture working its way up through the slab can dampen carpet, warp wood or laminate, loosen tiles, or leave a dark stain on a hard floor. Flooring that buckles or feels soft underfoot near a wall or in one room, with no spill to explain it, deserves a closer look.

6. Mould or a Musty Smell

Constant moisture under a floor creates the conditions mould needs. A musty smell that will not go away, mould on baseboards or low on a wall, or a room that always feels damp can all point to water coming up from below. Mould can keep growing even after the pipe is fixed if the damp materials are not dried out, so this sign is worth acting on quickly.

7. Cracks in Floors or Walls

A leak saturates the clay soil under the slab, and saturated clay loses some of its load-bearing capacity. The result can be small cracks in the floor, diagonal cracks in drywall, or doors and windows that start sticking. Not every crack is a slab leak — Olathe's clay soil moves with the seasons on its own — but new cracks that appear together with other signs on this list should be checked.

8. The Meter Test Shows Water Moving

The meter test, described below, is the most direct home check you can do. If the meter moves while every fixture in the house is off, water is leaving your system somewhere. That does not tell you where the leak is, but it confirms that you have one, and it is the result a detection visit starts from.

9. Soggy Soil or Unusually Green Patches Outside

Water escaping under the slab can surface outside the foundation, leaving soil that stays soggy after dry weather, or a patch of lawn that grows faster and greener than the rest. Look along the foundation line and in the yard near where the water line enters the house.

Free 15–20 Minute Meter Test

You can do this test yourself, and it costs nothing. First, turn off every tap, toilet, shower, dishwasher, washing machine, ice maker and irrigation system — anything that uses water. Make sure nobody in the house uses water during the test. Go to your water meter and write down the reading, including the small dial or leak indicator if your meter has one. Wait 15 to 20 minutes without using any water, then read the meter again. If the reading changed, or the leak indicator moved, water is flowing somewhere in your system. Take a photo of both readings. That photo, plus your recent water bills, is useful information for a detection visit — and if the meter did not move, you have ruled out a running leak for now, which is useful too. If the test is positive, call (913) 369-6679. Our Olathe slab leak repair team can pressure-test the lines and pinpoint the leak with acoustic listening and thermal imaging — see how slab leak detection works for what happens on that visit.

What to Do Next

One sign on its own is worth watching. Two or more, or a positive meter test, is worth a detection visit. Detection in Olathe has a typical range of $150–400, averaging about $280, and it gives you a confirmed answer before any concrete is opened. Photograph any warm or damp areas and note where they are — that helps the technician start in the right place. And if water is pooling, a wide area of floor is hot, or the meter is spinning fast, shut off the main water supply and call us right away.

Frequently Asked Questions

How do I know if I have a slab leak?

Look for a water bill spike, warm spots on the floor, the sound of running water with everything off, low water pressure, damp or warped flooring, a musty smell, cracks, or soggy soil outside. The most reliable home check is the water meter test: turn off all water for 15 to 20 minutes and see if the meter moves.

How urgent is a slab leak?

A slab leak is urgent because it runs 24 hours a day, wasting water and soaking the soil under your home. A leak caught early usually means a smaller repair; a leak left for weeks or months can damage flooring, encourage mold, and affect the soil that supports the slab. If you have two or more signs, get a detection test promptly.