7 signs of a slab leak

By Steve, owner of Steve's Plumbing Ventura, a licensed plumbing contractor.

The 7 most common signs of a slab leak are a warm spot on the floor, the sound of running water with everything off, a water meter that keeps moving, an unexplained jump in the water bill, damp or damaged flooring, low water pressure, and a water heater that runs constantly.

A slab leak is a leak in a water line under a concrete foundation. Many Ventura homes are built slab-on-grade, so these signs are worth knowing.

1. A warm or hot spot on the floor

A warm patch on tile, wood or concrete means a hot water line is leaking under it. It's the clearest sign of a slab leak and often shows up in kitchens, bathrooms and hallways where hot lines run. Pets often lie on the spot.

2. The sound of running water

Hissing or trickling from under the floor or inside a wall, with every tap, toilet and appliance off, means water is escaping a pressurized line. It's easiest to hear at night when the house is quiet.

3. A water meter that keeps moving

With all water use off, the meter should stand still. If the dial or leak indicator moves, water is leaking somewhere between the meter and your fixtures. Ventura Water customers with smart meters can also check hourly use and leak alerts online through Web Connect.

4. A sudden jump in the water bill

A bill much higher than the same month last year, without a change in household use, is often the first sign of a hidden leak. Ventura Water has a leak adjustment policy, so keep your repair invoice.

5. Damp, warped or cracked flooring

• Damp carpet or padding with no spill nearby.
• Wood or laminate floors that cup or buckle.
• Cracked tile or grout lines that open up.
• Musty smells or mold along baseboards.

6. Low water pressure

A large leak diverts enough water to lower the pressure at faucets and showers. A sudden drop across the whole house, rather than at one fixture, points to the supply line.

7. A water heater that runs constantly

When a hot water line leaks under the slab, the water heater keeps refilling and reheating. You may hear the burner come on often, see higher gas or electric bills, or find the tank warm all the time.

How to confirm a slab leak

1. Turn off all water use, including irrigation and the ice maker.
2. Check the meter. Note the reading or watch the leak indicator for 30 minutes.
3. Close the water heater's cold inlet valve and check the meter again. If it stops, the leak is on the hot side.
4. Call a plumber to pinpoint the exact spot with acoustic and thermal equipment.

What to do if you think you have a slab leak

Act quickly. A running slab leak wastes water and can wash out the soil under the foundation. If water is surfacing or the hot side is leaking, shut off the main valve and call. Our slab leak repair page explains spot repair, reroute and repipe options.

Why slab leaks happen in Ventura

Slab leaks in Ventura come from aging pipe, very hard water and ground movement. The median Ventura home was built in 1973, according to Census data, and Ventura Water's sources average 15 to 37 grains per gallon of hardness. Copper lines under a slab also expand and contract against concrete and gravel with every hot water draw.