Callers who find a slab leak tend to say the same things: "I have water coming up under my floorboards" and "I had to turn off the water at the meter to stop it." The first hour matters less than people fear, but a few steps in the right order save water, damage and time.
1. Decide how bad it is
- Water is coming up through the floor or concrete, or pooling inside: shut the water off now (step 2).
- No visible water, but the meter moves or you hear running water: you have time. Skip to step 3, but check the floor through the day.
2. Shut the main valve
Most houses have a shutoff where the line enters the house, often near a front hose bib. Turn it clockwise until it stops. If you can't find it, or it won't turn, the meter box usually has a shutoff, but in many areas that valve belongs to the utility and needs a meter key. If you use it, do so carefully, and tell the utility if anything breaks.
With the main off, the leak stops feeding. You'll be without water until a plumber isolates the problem, so fill a few jugs first if you can.
3. If a floor spot is warm, shut the hot side
A warm floor means the hot line. Close the cold-water inlet valve on top of the water heater. That stops the heater from refilling, so the hot side can't keep pushing water into the slab, and you still have cold water at the taps. For gas or electric settings, follow the heater manufacturer's instructions. More on this in hot water slab leaks.
4. Run the meter test
With fixtures off, check the leak indicator on the meter. Then close the house valve and look again. This tells you whether the leak is in the house or in the yard line. The full method is in the water meter leak test.
5. Photograph everything
- Wet floors, stains and warped boards
- The meter reading, with a timestamp
- Any water seeping at the slab edge or garage
- Recent water bills
These help the plumber and any insurance claim. Most policies want prompt notice, so call your insurer early. Slab leaks and homeowners insurance covers what to ask.
6. Move what can be damaged
Lift rugs, move furniture off damp carpet, and get electronics and boxes off the floor. Don't pull up flooring yet. The plumber may want to see where the water shows before anything moves.
7. If you rent, tell the owner in writing
Text or email the landlord or property manager with photos and the time you noticed it. The owner usually arranges the repair. See slab leaks for renters and landlords.
8. Call, and describe what you found
When you call, describe where the water shows, what the meter did, whether a floor spot is warm, and roughly how old the house is. Calls are answered during set hours, listed on the call page. Outside those hours, keep the main shut and call when the line opens.
What not to do
- Don't chip at the concrete to look for the pipe. Finding the leak takes equipment, and a guess can mean a bigger repair. Slab leak detection explains why.
- Don't leave the main off for days without a plan. A plumber can often isolate the leaking branch and restore water to part of the house.
- Don't agree to a repair without hearing the options. Spot repair, reroute and repipe each fit different houses. The home page compares them.
Two more questions
Should I turn off the water heater?
If the leak is on the hot side, close the cold-water inlet on top of the heater. Whether to also turn off its gas or power depends on the model, so follow the manufacturer's instructions for a heater with its water supply shut.
Can I use bleach or fans on the wet area?
Drying the surface is fine, but it won't fix anything underneath. Large wet areas, soaked carpet or wet drywall are a water damage job. Tell the plumber and your insurer about them.
Keep reading
- Running Water Under the Floor When Nothing Is OnThat trickle under the floor at night: the innocent causes to rule out first, and what it means when it won't stop.
- Why So Many Older Orange County Slab Houses Spring LeaksCopper under concrete, decades of hot-and-cold cycling, and water chemistry: what's behind slab leaks in older OC houses.