Signs that water may be leaking under your slab
A plumber finds a slab leak by combining a meter test, listening equipment, thermal imaging and pressure testing. You can do the first check yourself. Slab leaks hide under concrete, so the clues show up on the floor, the walls and the water bill. Two or three signs together are a strong reason to call.
Many Gulf Coast homes are built on a concrete slab, so supply lines often run through or under the floor. When one of those lines pinholes or cracks, the water has to go somewhere.
- A warm patch on the floor, which can mean a leaking hot line.
- The sound of running or hissing water when every fixture is off.
- Damp or lifting flooring, musty smell or mildew near baseboards.
- Cracks that open along a floor line or tile that suddenly loosens.
- A water bill that climbs with no change in use.
- Low pressure at several fixtures at once.
Try the meter test first
This takes ten minutes and costs nothing. Turn off every tap, the ice maker and the irrigation system. Find your water meter and look at the small leak indicator or the sweep hand.
Shut everything off
No running appliances, no one using water. Close the irrigation zone valves too.
Read the meter
Note the digits, or watch whether the small triangle or dial is turning.
Wait an hour or two
Do not use any water. Come back and read again.
Compare
Any movement means water is going somewhere. Check toilets and outdoor faucets before assuming a slab leak.
Meter still moving with everything off?
Call the 24/7 line and describe what you see. A plumber can come out and pinpoint the leak.
How plumbers pinpoint the break
| Method | What it detects | Good for |
|---|---|---|
| Acoustic ground microphone. | The sound of water escaping a pressurized line. | Locating the loudest point on the floor. |
| Thermal camera. | Temperature differences on the floor surface. | Hot water lines that heat the concrete. |
| Pressure test. | Whether a line holds pressure when isolated. | Deciding which line is leaking. |
| Tracer gas. | A harmless gas that escapes at the break. | Leaks the microphone cannot isolate. |
| Moisture meter. | Dampness in walls and flooring. | Confirming spread and damage. |
Good detection avoids guesswork. A plumber often combines two or three methods, because each one has blind spots. The goal is to mark the leak so any repair opens a small hole, not a large trench.
Slab leak or a different leak?
Not every wet floor is a slab leak. A failing toilet seal, a leaking shower pan, a dripping water heater and a sweating drain line can look alike. A plumber rules these out first because they are easier and cheaper to fix.
Drain leaks and supply leaks also behave differently. A supply leak keeps the meter moving with everything off. A drain leak shows up only when water is running down the pipe, so the meter test stays still.
What happens after the leak is found
Repair choices depend on where the break is and what the pipe is made of. Spot repair works for a single failure. A reroute sends the line through walls or the attic and abandons the slab section. Repiping replaces the whole run when pipes are failing in several places.
Ask for the options with the trade-offs in plain words. The slab leak repair page explains each path, and a leak detection visit comes first so you know what you are repairing.
Lynn Haven specifics worth knowing
The City of Lynn Haven runs its own water system, with deep wells in the Floridan Aquifer serving most customers, according to the city's 2024 Annual Water Quality Report. That report does not list water hardness, so test your own tap if mineral scale is a concern. Questions about the meter or your account go to the city's Public Utilities Department.
If detection points to a leak outside the house, call 811 before any digging. The city's utilities page says the same, and Sunshine 811 is the statewide service that marks buried lines. A saw cut in a driveway or a yard trench both count.
Insurance, and what it usually covers
Insurance often covers sudden, accidental water discharge, and it often does not cover wear or long-term seepage. The line between the two matters, so check your policy and report the damage promptly. A written leak detection report with photos helps your claim.
Ask your insurer whether the cost of finding the leak is covered separately from the repair. Policies differ, and a slab leak may be treated differently from a burst pipe in a wall.
Where to go from here
The warning signs are the same whether the house is in Springfield or Southport. Do not wait on a bill that keeps rising. Water that escapes under a slab can damage flooring, baseboards and the framing above it.
Call the 24/7 line and describe the signs and the meter reading. The dispatcher will confirm the right equipment for the job and book a licensed plumber.
Frequently asked questions
Look for a warm floor spot, the sound of water with everything off, damp flooring, mildew and a rising bill. Then run the meter test. A turning meter with all water off is a strong indicator.
Yes. Acoustic microphones, thermal cameras, pressure tests and tracer gas locate the leak from the surface. Only the confirmed spot is opened for repair.
If water is surfacing, soaking floors or the meter spins fast, shut off the main valve and call right away. A slow leak is less urgent but gets worse with time.
Policies differ. Sudden, accidental discharge is often covered and long-term seepage often is not, so check your policy before you book.
Call 811 first. Sunshine 811 is the statewide service that marks buried utility lines, and the city's utilities page also tells residents to call 811 before digging.