Slab leak symptoms: the signs, and what to do right now

Short answer: The clearest signs of a slab leak are a warm spot on the floor, the sound of water running when every tap is off, and a water bill that jumped for no reason. One of those alone could be something simpler. Two together usually isn't, and the water meter test below will tell you in half an hour whether water is leaving your plumbing somewhere it shouldn't.

What a slab leak is, and why North Texas gets so many

A slab leak is a broken water line under your home's concrete foundation. The pipe cracks, wears a pinhole, or pulls apart at a joint, and the water goes into the soil under the house or comes up through the slab.

They're common here because of the ground. Collin County sits on clay that swells when it rains and shrinks in a drought. The soil under your foundation moves with it, year after year, and that movement is hard on rigid water lines running beneath the slab. Sooner or later one of them gives.

The 8 signs of a slab leak

1. A warm spot on the floor. This is the one people remember, and it points to the hot water line. It often shows up in a hallway, on tile, or as a patch of carpet that feels warm under bare feet. It stays warm even when nobody is using hot water.
2. Running water you can hear with everything off. If you hear water moving in the walls or under the floor and nothing in the house is running, it's going somewhere.
3. A water bill that jumped. No pool to fill, no new sprinkler schedule, no houseguests, and the bill still went up.
4. The water heater running more than it should. When the hot line leaks, the heater keeps replacing what escapes. You may hear it firing over and over at times when nobody is using water.
5. Damp flooring or a musty smell with no source. Damp carpet, wood that cups or buckles, tile that lifts or sounds hollow, or a mildew smell you can't trace to any fixture.
6. New cracks. Cracks in walls, ceilings, baseboards or the slab itself can come from soil washing out or shifting under the foundation. Clay movement causes cracks too, so this one means more when it shows up alongside the others.
7. Water pressure that quietly dropped. Showers feel weaker and the kitchen faucet doesn't have the push it used to.
8. Wet ground near the foundation. Soggy soil or standing water along the outside of the house when it hasn't rained.

The water meter test

This tells you whether water is leaving your plumbing at all. It doesn't tell you where.

1. Turn off every tap and everything that uses water: the dishwasher, washing machine, ice maker, sprinklers, and the softener if you have one.
2. Find the water meter, usually in a box near the street. Write down the reading, or watch the small leak indicator if your meter has one.
3. Wait 15 to 30 minutes without using any water inside or out.
4. Check again. If the reading changed or the indicator moved, water is going somewhere.
5. Now close the main shutoff to the house and check once more. If the meter stops, the leak is on the house side of the shutoff, and that includes the lines under the slab. If it keeps moving, the leak is probably on the line between the meter and the house. That is a water line repair, not a slab leak.

Hot line or cold line?

A hot line leak usually gives itself away with a warm spot, and it keeps the water heater working to replace what escapes, so you pay for the water and again for the energy to heat it. A cold line leak has no warm spot and doesn't touch the water heater. It can run for months before the bill or the sound gives it away. Either one is washing out soil under your foundation the whole time.

What to do right now

1. If water is coming up onto the floor, close the main shutoff to the house.
2. If you think it's the hot line and you can't get to the main, closing the cold water supply valve on the water heater stops water feeding the hot side.
3. Take photos of the wet areas, any cracks and the meter reading. Your insurance carrier will ask for them.
4. Call your insurance carrier so they know before any work begins.
5. Move rugs and furniture off wet floors so they stop soaking up water and the floor can start to dry.
6. Call a plumber. A slab leak doesn't stop on its own.

Finding a warm patch in the hallway is unsettling, and it's tempting to wait and see if it goes away. It won't, and every day it runs is more soil gone from under the slab.

What not to do

• Don't open the floor yourself. Cutting concrete in the wrong place just adds a second repair.
• Don't call a foundation company first. If the cause is a broken water line, they can't fix the pipe, and you want the water stopped before anyone judges the foundation.
• Don't spend money on new flooring until the leak under it is fixed.

How a slab leak gets fixed

We start by evaluating the plumbing and testing to confirm whether a line under the slab is involved. Then we explain the options and the price for each, in writing, before work begins. There are usually three:

• A spot repair opens the slab at the break, repairs the pipe, and patches the concrete. It fits when the rest of the line is sound and this is its first failure.
• A reroute abandons the line under the slab and runs new pipe through the walls or the attic. No concrete gets opened.
• A repipe replaces the whole line. It makes sense when the same line has already failed more than once.

The trade-offs between them, and what drives the cost of each, are on our slab leak repair page.

Does homeowners insurance cover a slab leak?

It depends on your policy. Many policies treat the pipe and the damage it caused as two separate things: some pay to open and restore the floor and for the water damage, but not for the pipe repair itself. Call your carrier before work begins, ask what your policy covers, and keep the photos and the paperwork from the plumbing evaluation. That is usually what a claim asks for.

Slab leak questions we get asked

Can I wait a few days to see if the warm spot goes away?

No. A warm spot means hot water is escaping under the slab right now, and it will keep going until the line is repaired. Waiting adds to the water bill, the gas or electric bill, and the soil washing out under the foundation.

Can a slab leak be fixed without jackhammering the floor?

Often, yes. A reroute leaves the slab alone: the old line is abandoned and new pipe runs through the walls or attic. Whether that's the better choice depends on the house and the pipe, and we'll tell you which one we would do in our own home.

Do all slab leaks make a warm spot?

No. Only hot line leaks do. A cold line leak has no warm spot, so it tends to show up as a higher water bill, the sound of running water, or a meter that moves during the test above.

Can a slab leak damage my foundation?

It can. Water running under the slab washes out the soil that supports it, and that can lead to settling and cracks. Fixing the leak stops the washout. If you're worried about the foundation itself once the plumbing is fixed, that's a question for a foundation specialist.

How do I know it's under the slab and not somewhere else?

The meter test tells you there's a leak, and where the signs show up narrows down where it is. A warm spot or a damp floor with no plumbing fixture nearby points to a line under the slab. A wet ceiling or a stain on a wall usually points to a pipe in that wall or above it.

Will my whole floor have to come up?

Usually not. A spot repair opens only the section above the break, and a reroute doesn't open the floor at all. How much flooring needs replacing after that depends on how long the leak ran and what the floor is made of.

When to call us

Call if the meter moved during the test, or if you have two or more of the signs above. Genzel Plumbing is a family-owned plumber in McKinney working under Texas Responsible Master Plumber license RMP-23766, and we've served Collin County homes since 2001. You get the options and the prices in writing before work starts, and financing is available for repairs you didn't plan for. Call (972) 238-5585.