6 Signs You Have a Costly Foundation Slab Leak

Updated: Sep. 29, 2023

If your home is built on a concrete foundation slab, watch for signs that water may be lurking beneath the surface.

After enduring an eight-month remodel that included tiling both bathroom showers, replacing all 1,800-sq. ft. of flooring and adding a fresh coat of interior paint throughout, my fiancé and I assumed we could kick back and enjoy our freshly updated home. And we did — for about a month.

Then, all of a sudden, the newly installed luxury vinyl flooring planks began popping up in a few rooms. We had the installer and manufacturer over several times. But nobody was willing to claim responsibility, and the problem rapidly spread.

We began noticing other signs, too, but didn’t connect the dots until a plumber, brought in for a third opinion, immediately recognized the issue: a slab leak. It would be another week before we learned just how much damage one tiny hole in our buried hot water line caused.

We were forced to file our first-ever homeowner’s insurance claim, move all our belongings into storage and live out of a hotel while the leak was fixed. The house had to be dried out; the floors, cabinets and baseboards demolished and replaced; and the walls repainted.

Learn more about what a slab leak is and how to spot the signs.

What Is a Slab Leak?

Slab leaks only occur in homes with a concrete slab foundation instead of a pier-and-beam design. A slab leak is a plumbing leak that occurs under the concrete slab, where the plumbing is buried. Slab foundations are a common construction choice in Southern and Western states with warm climates, where the freezing and thawing of the ground is less of a concern.

“Because the slab is supporting the entire weight of your home, when a plumbing leak occurs, water leaks under the concrete slab, ultimately compromising the home’s foundation,” says Shane Jaeger of Benjamin Franklin Plumbing in Plano, Texas.

“There can be many possible causes for a slab leak, including corrosion due to pipes encountering other metals in the soil, built-up pressure on the underground pipes or even abrasion due to pipes rubbing against another hard surface.”

My plumber explained it was a common problem in older homes, where pipes have simply become vulnerable due to age. My 1975 home with original pipes was more or less right on track for just such an occurrence. And it had nothing to do with our remodel. The pinhole-sized leak that caused so much damage was simply bad timing.

Slab Leak Repair Cost

Our insurance claim came in at a little more than $75,000. Our deductible was only $2,500, although we did spend more for upgraded materials, choosing porcelain tile over luxury vinyl flooring this time around.

In general, the cost to remedy a slab leak depends on a variety of factors, including the state of the pipes and when you identify the problem. It could range from $1,200 to $10,000.

“Fixing a leak early is cheaper than repairing a foundation,” says Chris McLaughlin, division sales manager at Groundworks, the largest foundation services company in the U.S. “It’s never cheaper to fix than it is today.”

Six Signs You Have a Slab Leak

The sooner you spot a slab leak, the better. If you experience any of the following warning signs, call your plumber immediately, McLaughlin says. This way they can assess the situation and propose a solution to mitigate further damage to your property.

Hot spots on the floor

If your dog or cat starts lounging on previously ignored spots on your floor, they may be enjoying the cozy warmth of hot water. Feel it to see if it’s unusually warm. “Slab leaks are often from hot water lines,” says Jaeger. “The hot water begins to leak through the slab of your home up to the flooring above, causing the floor to be warm or hot to touch.”

Unusually high water bills

Check your water bill each month, and don’t ignore even a small increase that isn’t otherwise justified. “If you notice you’re suddenly paying more than normal for water without an increase in usage, you might have a leak,” says McLaughlin. “It’s not uncommon for homeowners to experience a 25-percent jump in water bills due to the constant dripping.”

Sound of running water

While it’s not uncommon to hear running water as it moves throughout your home’s plumbing system, it is concerning to hear whooshing water when all water appliances and faucets are off, says Jaeger. The unexpected sound could be from a pipe leak somewhere in the home.

Floors warping or planks popping

“Wood floors can soak up a lot of water before you notice any dampness so, it’s often the warping of the wood floor that is noticed before actual water,” Jaeger says.

Mold and mildew under carpets

It can begin to grow after just 24 to 48 hours of water exposure, Jaeger says. “If you notice brown, green, or black stains on your carpets, this could be a clear sign that water is seeping into your home’s flooring level,” he says. You may notice a sour odor, too.

Water pooling around your home

Pooling water is never a good sign, McLaughlin says. It may indicate a foundation pipe leak.

How To Fix a Slab Leak

Leak detection specialists outfitted with special equipment can pinpoint your slab leak location; it’s not always where the water shows up. There are four options to fix it:

  1. Reroute the pipe: This is often the cheapest and least disruptive fix, McLaughlin says. That was true for us. The leaky pipe was right under our freshly remodeled guest bathroom shower, which would’ve cost thousands to replace had they jackhammered through it to get to the leak. It made more sense to reroute the above-ground plumbing. A plumber reroutes a pipe by adding a new pipe that bypasses the faulty one. The old pipe remains where it is, but water no longer flows to it. In our case, this involved cutting into multiple walls and spots in the ceiling, but drywall is much cheaper to replace than tile. Cost: $1,200 to $5,000.
  2. Repair the leak through the slab: This option involves breaking the concrete and digging a hole to access the leak. Jaeger says it may be cheaper than other methods, but it’s disruptive inside your home. (Think: a hole with concrete dust flying everywhere). Cost: $1,500 to $3,500.
  3. Repair the leak from under the slab: In some parts of the country, you can access the leak from a tunnel under the home, Jaeger says. This is less destructive inside the house and more convenient to most homeowners, but can be more expensive depending on the leak location. Cost: $2,500 to $10,000.
  4. Reline the pipe: This final option involves lining the inside of the pipe with a coating, which Jaeger says provides peace of mind by making another leak rare. However, it’s best for small leaks, and expensive and disruptive to the inside of the home. Cost: $2,000 to $8,000.

Before you choose how to fix a slab leak, ask your plumber if this could happen again.

“In our experience, most of our customers who have a slab leak only have one,” says Jaeger. “But there are situations where a customer will have multiple leaks, either at the same time or over a period of years. That’s usually when we discuss the whole house re-route or relining.”

When weighing this decision, which can cost $7,000 or more because it’s preventive, you’ll also take into account why the leak occurred. Was it because of pipe corrosion, or a rock rubbing against the pipe? If the pipes are starting to deteriorate, then Jaeger says you definitely want to look at whole-house solutions.