Signs of a Slab Leak and How to Check Your Laredo Home

Last updated: November 14, 2026

A slab leak is a leak in a water line that runs under a home's concrete slab. You can't see it, so it can run for a while before anyone notices. The good news: there are clear signs, and a simple meter test tells you whether water is going somewhere it shouldn't.

The signs

• Warm spots on the floor. A leaking hot-water line can warm the concrete above it. You may feel it barefoot.
• Running water you can't find. A hiss or trickle when every tap is off.
• A higher water bill without any change in how you use water.
• Low water pressure throughout the house.
• Cracks in lower walls or baseboards that start small and grow.
• Damp carpet or a musty smell near a wall, even after it dries.

These signs come from This Old House's guide to slab leaks. One sign alone isn't proof. Two or three together, plus a meter that keeps moving, make a leak very likely.

Check your meter today

Laredo Utilities explains how to read the water meter, which is in a box near the curb or sidewalk with a metal lid marked "Water Meter" or "City of Laredo Water Meter."

1. Turn off everything that uses water, inside and out: taps, toilets, the washer, the ice maker and sprinklers.
2. Look at the meter. On a dial meter, watch the large hand. On a digital meter, shine a light on the display and read the flow rate.
3. Movement means a leak. If the hand moves or the flow is above zero, water is going somewhere.
4. Check for slow leaks. Write down the reading, wait 20 minutes without using water and read it again.

The EPA suggests a longer test: two hours without using water. If the reading changed, you probably have a leak.

Rule out the toilet first

Toilets are a common hidden leak. The EPA's test: put a few drops of food coloring in the tank and wait 10 minutes without flushing. If color shows up in the bowl, the toilet is leaking. Flush right after so the color doesn't stain. If the toilet is the leak, it's a much smaller fix than a slab leak.

How a plumber finds it

A plumber narrows it down by testing parts of the system and using equipment such as a camera inside the line, so they open as little of the floor as possible. Ask how they'll locate the leak and what that step costs on its own. HomeAdvisor's national figure for leak detection is about $280, with most between $150 and $400.

How slab leaks are repaired

According to This Old House, the main options are:

• Spot repair: opening the concrete over the leak and replacing that section of pipe.
• Lining the pipe from inside to seal the leak.
• Rerouting: running a new line through the walls or attic and leaving the slab alone.

The right choice depends on where the leak is, the condition of the rest of the pipe and how many leaks there have been. If leaks keep coming back, ask about repiping.

What repairs cost

HomeAdvisor's national average for slab leak repair is $2,280, with most jobs between $630 and $4,400, depending on how the leak is reached and fixed. Prices in Laredo can be different; the plumber confirms the price before starting.

Why it's worth acting soon

The EPA estimates that leaks in an average household waste more than 9,300 gallons a year. A leak under a slab can also soak flooring and walls before you see anything.

Questions to ask the plumber

1. How will you confirm and locate the leak, and what does that cost?
2. What are my repair options, and what does each cost, in writing?
3. Will you need to open the floor, and who repairs it afterward?
4. Does the job need a city permit?
5. What's your license number? Look it up before work starts.

Related

• Leaks, slab leaks and burst pipes
• A pipe burst: what to do now
• Installation and replacement, including repiping
• How to hire a plumber in Laredo

Before you hire, check the license

Sources

• This Old House, "Signs of a slab leak" (updated May 27, 2026)
• Laredo Utilities, "Understanding your water meter"
• U.S. EPA WaterSense, "Fix a Leak Week" (updated Mar. 13, 2026)
• HomeAdvisor, "Slab leak repair cost" (2025)