Signs of a Slab Leak and What to Do About It

Many homes are built on a concrete slab, with water lines running in or under the concrete. A slab leak is a leak in one of those lines. Because the pipe is hidden under the floor, the water can soak into the ground or the slab for a long time before anything shows on the surface.

Slab leaks can be on the hot side or the cold side, and the signs are a little different for each.

Watch for any of these:

• A water bill that goes up while your water use stays the same.
• The sound of running water when every faucet and appliance is off.
• A warm spot on the floor, often a sign of a leak on the hot water line.
• Damp carpet, cupped wood flooring, or loose tile with no spill to explain it.
• New cracks in flooring or in the walls.
• A musty smell or mold near the floor.
• Lower water pressure throughout the house.
• A water heater that runs more than it used to.

Your water meter is the best tool you have. It takes about 15 minutes:

1. Turn off every faucet, toilet, ice maker, sprinkler, and appliance that uses water.
2. Find your water meter, usually in a box near the street, and note the reading.
3. Wait 15 minutes without using any water.
4. Check again. If the numbers moved or the leak indicator is spinning, water is going somewhere.

A moving meter does not prove the leak is in the slab. It could be a running toilet or an outdoor line. But it does tell you there is a leak worth finding.

Pipes under a slab can wear where they rub against concrete or gravel, especially hot lines that expand and contract every time they heat up. Corrosion, poor original installation, and ground movement under the foundation can all play a part. Older homes are more likely to have them, but they can happen in newer homes too.

If water is coming up through the floor, turn off the main water valve to the house if you can reach it safely. If the leak seems to be on the hot side, turning off the water supply to the water heater can help too. Then call a licensed plumber.

Do not start breaking up flooring to look for it. Pinpointing the leak first keeps the repair smaller.

There are two main options:

• Spot repair: open the slab directly over the leak and repair that section of pipe. This works well when the rest of the pipe is in good shape.
• Reroute: abandon the leaking line and run a new one through the walls or attic. This avoids breaking concrete and is often the better choice when the pipe is old or has leaked before.

We will explain which option makes sense for your home and let you choose. Either way, we find the source before we open anything up.

Water running under a slab for a long time can wash out soil and contribute to settling, and it can cause mold and flooring damage inside. That is the main reason not to wait. The sooner the leak is found, the smaller the repair and the cleanup.