5 Signs You Have a Slab Leak (And What to Do Next)

If you own a home in Houston, there's a good chance your house sits on a concrete slab foundation. It's the most common foundation type in the Greater Houston area — and for good reason. Slab foundations work well in our flat terrain and high water table. But they come with a hidden risk: slab leaks.

A slab leak is a water leak that occurs in the plumbing pipes running beneath or within your concrete foundation. Because these pipes are buried under inches of concrete and soil, slab leaks can go undetected for weeks or even months — quietly causing damage the entire time.

The good news? Slab leaks almost always leave clues. Here are the five most common signs of a slab leak, what causes them, and what you should do if you suspect one in your Houston home.

1. Hot Spots on Your Floor

One of the most distinctive signs of a slab leak is a warm or hot spot on your floor. If a hot water supply line beneath the slab develops a leak, the escaping hot water heats the concrete above it. You might notice a specific area of tile, laminate, or hardwood that feels unusually warm compared to the rest of the floor.

This is especially noticeable in rooms with tile flooring, which tends to feel cool naturally. If you're walking barefoot and one section feels noticeably warm, pay attention. In Houston's climate, where we run air conditioning most of the year, a warm spot on the floor is particularly easy to feel.

Hot spots are most commonly caused by leaks in the hot water supply line, which runs from your water heater to your fixtures. Copper pipes — still common in many Houston homes built before the early 2000s — are especially vulnerable to corrosion from our mineral-heavy water and the chemicals in the surrounding soil.

2. The Sound of Running Water When Everything Is Off

If you hear water running or a faint hissing sound when all faucets, showers, and appliances are off, something isn't right. This is one of the earliest signs of a slab leak that homeowners report.

To test this yourself, turn off every water-using appliance and fixture in your home. Make sure the dishwasher isn't running, the washing machine is off, and no toilets are filling. Then stand in a quiet area — especially near the center of your home — and listen. A persistent rushing, hissing, or dripping sound is a strong indicator that water is escaping from a pipe somewhere.

You can also check your water meter. With everything off, go outside and look at your meter. If the dial is still moving or the flow indicator is spinning, water is flowing somewhere it shouldn't be. This doesn't confirm it's a slab leak specifically, but it confirms you have a leak that needs professional leak detection.

3. Cracks in Your Foundation or Walls

Water is powerful. When a pipe leaks beneath your slab, the water saturates the soil underneath your foundation. In Houston, where our soil is predominantly heavy clay, this creates a serious problem. Clay soil expands dramatically when wet and contracts when dry. This constant expansion and contraction creates uneven pressure under your foundation.

Over time, this can cause your foundation to shift, settle, or heave. The visible signs include:

• Cracks in your interior or exterior walls, especially near doors and windows
• Cracks in your baseboards or crown molding
• Doors and windows that suddenly stick or won't close properly
• Visible cracks in the slab itself (if exposed in a garage or utility area)
• Uneven or sloping floors

Not every crack means you have a slab leak — some settling is normal, especially in newer Houston homes. But if cracks appear suddenly, get worse over time, or show up alongside other symptoms on this list, it's time to call a slab leak detection specialist.

4. An Unexplained Spike in Your Water Bill

Your water bill should be reasonably consistent from month to month. If you see a sudden jump — say $50 to $100 more than usual — and you haven't changed your water usage habits, a hidden leak is the most likely culprit.

Even a small slab leak can waste thousands of gallons of water per month. A pinhole leak in a copper pipe running at constant pressure can lose 20 to 30 gallons per day — that's over 600 gallons per month. A larger crack or separation can waste far more.

If your water bill has been climbing steadily or jumped dramatically, take these steps:

1. Check for obvious leaks — running toilets, dripping faucets, irrigation system issues
2. Do the water meter test described above (turn everything off and check if the meter is still moving)
3. Compare your bills over the last 6 to 12 months to spot the trend
4. Call a professional leak detection company if you can't find the source

In many cases, your water provider can also help. The City of Houston and surrounding MUDs (Municipal Utility Districts) will sometimes flag accounts with unusually high usage and may offer leak adjustments on your bill once the leak is confirmed and repaired.

5. Mold, Mildew, or Musty Odors

A slab leak creates a constant source of moisture beneath your home. In Houston's already humid climate, this is a recipe for mold growth. If you notice a persistent musty smell — especially near the floor level — or see mold or mildew forming on walls, baseboards, or carpet, a slab leak could be the source.

Mold can begin growing within 24 to 48 hours of exposure to moisture, and Houston's heat and humidity accelerate that timeline. Common signs include:

• Musty or earthy smell in certain rooms, especially bathrooms, kitchens, or utility rooms
• Dark spots or discoloration on baseboards or lower walls
• Carpet that feels damp or looks discolored in specific areas
• Warped or buckled hardwood flooring
• Peeling paint or bubbling wallpaper near the floor

Mold isn't just a property problem — it's a health issue. Prolonged exposure to mold can cause respiratory problems, allergic reactions, and other health concerns. If you suspect mold from a water leak, addressing the source of the moisture is the critical first step.

Why Slab Leaks Are So Common in Houston

Houston homes are uniquely susceptible to slab leaks for several reasons:

• Clay soil: Houston's expansive clay soil shifts with moisture changes, putting stress on buried pipes and causing them to crack or separate at joints.
• Copper plumbing: Many Houston homes built in the 1970s through early 2000s used copper pipes under the slab. Our water chemistry and soil conditions accelerate copper corrosion from the outside in.
• Slab-on-grade construction: With virtually every Houston home built on a slab, the plumbing runs through or beneath the concrete — making leaks harder to detect and access.
• Water pressure fluctuations: Municipal water pressure changes can stress aging pipes, especially at elbows, joints, and fittings.

What to Do If You Suspect a Slab Leak

If you're seeing one or more of the signs above, don't wait. Slab leaks get worse over time — never better. Here's what we recommend:

1. Don't panic. A slab leak is a fixable problem. Catching it early saves money and reduces damage.
2. Do the water meter test. Turn everything off and check for movement on your meter to confirm a leak exists.
3. Document what you're seeing. Take photos of cracks, water stains, mold, or warm spots. This helps both the leak detection technician and your insurance company.
4. Call a professional leak detection company. A specialist with thermal imaging, pressure testing, and acoustic equipment can pinpoint the exact location of the leak without tearing up your floor.
5. Contact your insurance company. Many homeowner policies cover sudden and accidental slab leaks. An insurance-ready leak detection report can support your claim.

At Exact Leak Detection HTX, we specialize in finding slab leaks quickly and non-invasively. Our slab leak detection service uses professional-grade thermal cameras, acoustic listening devices, and pressure testing equipment to locate the exact point of failure beneath your foundation. Every inspection includes a detailed report with photos, thermal images, and findings — built for homeowners and insurance companies alike.