We are paid when readers call a provider through this site. That never changes our advice. How we make money
Quick answer
The usual signs of a slab leak are a warm spot on the floor, the sound of running water with every fixture off, damp carpet or flooring near walls, low water pressure, and a water bill that jumps for no reason. [1][6] Start with your water meter: with all water off, a moving low-flow dial means you have a leak somewhere. [2] The meter cannot tell you the leak is under the slab, so check toilets first, then call a plumber who does leak detection. HomeAdvisor's June 19, 2026 guide puts detection at $150 to $400 and repair at $630 to $4,400. [6]
Do this first: check whether water is leaking at all
A slab leak is a leak in a water line under a concrete slab foundation. This Old House says it is specific to homes built on slabs, and often starts when copper water lines under the slab corrode. [1] You cannot see the pipe, so start with the one tool every house has: the water meter.
Turn off every faucet, toilet, appliance and irrigation system, and make sure no one uses water during the test. [2]
Find your water meter. The Saving Water Partnership says it is usually in the parking strip or sidewalk at the front or side of the house. [2]
Look at the low-flow indicator, the small dial that spins even when only a little water passes. If it is not moving, you do not have a continuous leak. If it is moving, you have a leak. [2]
If your meter has no low-flow dial, write down the reading and check it again later without using water. The City of Columbus suggests waiting 20 minutes to one hour, and EPA suggests checking before and after a two-hour period with no water use. [3][4]
Take photos of the meter readings, plus any damp spots and cracks, for your plumber and insurer. [1]
The Saving Water Partnership adds one limit: leaks that start and stop, like a running toilet, may not show up if they are not running when you check. [2] A still dial on one test does not rule everything out.
Warm floors and wet floors near power
If water is on the floor near outlets, cords or the electrical panel, do not walk into it. Turn power off at the panel only if you can reach it from a dry spot; otherwise call the utility or an electrician. This Old House also warns that prolonged contact with a hot spot over a leaking hot water line can be dangerous for young children and pets and may cause skin irritation or burns. [1]
What the meter test can and cannot tell you
The meter shows whether water is leaking, and the Saving Water Partnership's steps narrow it to inside the house, the irrigation system or the service line. It does not point to a slab. Here is the Saving Water Partnership's method, step by step. [2]
With all water off and the dial moving, close the main water shutoff valve for the house. Turn on an indoor faucet to make sure the water is off.
Look at the dial again.
If the dial stopped after you closed the shutoff, the leak is inside the house. The Saving Water Partnership says it is more than likely in your toilet.
If the dial is still moving and you have irrigation, shut off the irrigation. If that stops the dial, the leak is in the irrigation system.
If the dial still moves with water off to the house and the irrigation, the leak is in the service line between the meter and your shutoff valve.
What each meter result means (Saving Water Partnership), with next steps
With all water off
What it means
Next step
Dial does not move
No continuous leak right now
Test again later; leaks that start and stop may not show
Dial moves, then stops when the house shutoff is closed
Leak is inside the house, more than likely a toilet
Check every toilet first, then look for other signs
Dial stops only when irrigation is shut off
Leak is in the irrigation system
A plumber or landscaper
Dial keeps moving with house and irrigation shut off
Leak is in the service line between the meter and the shutoff valve
A plumber for the service line
Table source: [2] The toilet next step is the site's own suggestion, based on that page. A slab leak is one possibility when the leak is inside the house, but so are toilets, faucets and pipes in walls. Check the toilets first. EPA says to put a few drops of food coloring in the tank; if color shows up in the bowl after 10 minutes, the toilet leaks. [4] If toilets pass and the dial still moves, the signs below and a leak detection visit are the way forward.
Austin Water notes that property owners are responsible for service lines past the meter and for internal plumbing. [5] Your water utility can tell you where your side begins.
What are the signs of a slab leak?
No single sign proves a slab leak. Several together, plus a meter that keeps moving, make it likely. These are the signs This Old House and HomeAdvisor list, with what else could cause each one.
Common slab leak signs and other possible causes
Sign
What it can mean
Other possible causes
Warm or hot spot on the floor
This Old House says hot spots typically line up with the path of a leaking hot water pipe
Another heat source under the floor, such as heating ducts; ask the plumber
Sound of running water with everything off
This Old House says there could be a leak under the slab
A running toilet, or a leak elsewhere; This Old House notes a leak can be anywhere there are pipes, including behind drywall
Water bill jumps with no change in use
A continuous leak
Toilets, faucets, irrigation
Damp or wet carpet near walls or baseboards
Water seeping up from below; This Old House says dampness that keeps coming back can indicate an ongoing issue
Spills, pet accidents, a leak in the wall
Low water pressure throughout the house
Water escaping from a broken pipe
Clogged or damaged pipes
Cracks in walls or baseboards
Moisture from below
Structural movement; have it evaluated
Standing water around the foundation
Austin Water says it could mean underground pipes are damaged
Rain; This Old House says look for water that stays for days after dry weather
Musty smell
Ongoing moisture and possible mold or mildew
Other hidden leaks or high humidity
Table sources: This Old House, updated December 9, 2025 [1], HomeAdvisor [6] and Austin Water. [5] Third-column entries tied to This Old House are from its page; the rest (heating ducts, irrigation, humidity) are the site's own practical suggestions.
Listen for it. The City of Columbus describes a simple test: with all faucets off, press the tip of a long screwdriver, preferably 10 inches or longer, firmly against a faucet or exposed pipe and put your ear to the handle. If you hear running water, you have a leak. [3]
Check the bill. EPA says that if a family of four uses more than 12,000 gallons a month in a colder month such as January or February, there could be serious leaks. [4]
Corrosion. As pipes age they can corrode and leak. Copper and galvanized steel are especially prone to it.
Water chemistry. Highly acidic or alkaline water can speed up corrosion in metal pipes.
Shifting foundation. Soil movement, earthquakes and tree roots can press on the slab and the pipes under it.
Poor installation. Loose connections or low-quality pipe under the slab.
High water pressure. It puts added strain on the plumbing.
Abrasion. Debris or sediment in the water can wear through pipes over time.
This Old House says modern PEX plumbing resists many of these problems, but no pipe is immune. [1] HomeAdvisor's June 2026 guide says slab leaks are most common where the ground moves, such as earthquake areas and highly expansive soils. [6]
What to do while you wait for a plumber
Shut off the main water valve if you see significant water coming in or hear a strong rushing sound, as This Old House advises. For smaller leaks you may be able to skip this. [1]
Use as little water as you can until the leak is found.
Pull back wet rugs and move furniture off damp flooring.
Dry what you can. EPA says that if wet materials are dried within 24 to 48 hours of a leak, in most cases mold will not grow. [7]
Photograph the damp spots, cracks and meter readings, and call your insurer to ask how to report it. [1]
Call a licensed plumber who does leak detection. HomeAdvisor's June 2026 guide says to call a licensed plumber right away if you spot red flags such as warm or damp floors, standing water, sudden changes in water pressure, unusually high water bills or running water sounds with no fixtures in use. [6]
A plumber fixes the pipe. Wet flooring, baseboards and drywall are a separate drying job. Massachusetts guidance says to cut out and discard wallboard that has not dried within 48 hours. [8]
How slab leaks are found and fixed, and what it costs
Finding the exact spot comes first, so the repair opens as little concrete as possible. HomeAdvisor's slab leak guide, updated June 19, 2026, puts leak detection at an average of $280, with most homeowners paying $150 to $400. It puts the repair itself at an average of $2,280, with a typical range of $630 to $4,400, and says labor, at $500 to $4,000, is the bulk of the bill. [6]
Slab leak repair costs by method (HomeAdvisor, June 19, 2026)
Repair
Typical cost
Leak detection
$150 to $400
Pinhole leak
$150 to $800
Pipe leak repair
$250 to $850
Single burst pipe
$200 to $3,000
Reroute the line around the slab
$600 to $4,000
Cured-in-place repair
$80 to $250 per linear foot
Drain line leak repair
$800 to $5,000
Water damage repairs
$500 for minor subfloor repair to $15,000 or more
Table source: [6] What moves the price: where the leak is, the condition of the slab, local soil, and whether the plumber finds water damage or foundation problems. A reroute abandons the leaking line and runs a new one through the walls or attic, so the slab stays intact. HomeAdvisor says a minor, easy-to-reach leak can take about three hours to fix and a large or hard-to-reach one up to three days, with rebuilding flooring or cabinets adding weeks. [6]
Does homeowners insurance cover a slab leak?
It depends on the cause and the wording. Washington's insurance commissioner says homeowner insurance usually covers sudden leaks but may not cover gradual ones. [9] The sample HO-3 form posted by the Insurance Information Institute, an older Insurance Services Office form (HO 00 03 10 00), covers damage from an accidental discharge of water from within a plumbing system, unless the loss is otherwise excluded, and the cost to tear out and replace part of the building when needed to repair the system, but not the pipe the water escaped from. [10] That is a sample, not your policy.
Read your own policy's water damage section and exclusions, or ask your agent, before work starts. Photos of the meter readings and damage help either way.
When to call a pro
The meter still moves with every fixture off and the toilets ruled out.
A floor spot stays warm or damp with no other explanation.
Carpet, flooring or baseboards keep getting wet.
Water is near outlets, cords or the electrical panel.
Flooring or drywall is still wet after 24 to 48 hours. [7]
New wall or floor cracks show up along with the other signs. This Old House says to have wall cracks evaluated, since structural problems can cause them too. [1]
Common questions
How do I know if I have a slab leak?
Look for a warm or damp spot on the floor, running-water sounds with everything off, low water pressure and an unexplained jump in the water bill. [1] Then check the meter with all water off. A moving dial means a leak somewhere, not necessarily under the slab. [2]
Can I check for a slab leak myself?
You can confirm a leak exists. Turn off all water and watch the meter's low-flow dial, then close the main shutoff. If the dial stops, the Saving Water Partnership says the leak is inside the house, more than likely a toilet. [2] Pinpointing a leak under concrete takes a plumber's leak detection equipment.
How much does it cost to fix a slab leak?
HomeAdvisor's June 19, 2026 guide puts the average at $2,280, with most repairs running $630 to $4,400, and lists detection separately at $150 to $400. [6] Water damage repairs are extra.
Is a slab leak an emergency?
A fast one can be. This Old House says to shut off the main water valve if you see significant water or hear a strong rushing sound. [1] A slow leak still needs prompt attention. EPA says that if wet materials are dried within 24 to 48 hours, in most cases mold will not grow. [7]
Does homeowners insurance cover slab leaks?
Sometimes. Sudden leaks are usually covered and gradual leaks often are not, says Washington's insurance commissioner. [9] The Insurance Information Institute's sample HO-3 form covers tearing out part of the building when needed to repair the pipe, but not the pipe itself. [10] Check your own policy.
How long does it take to fix a slab leak?
HomeAdvisor says a minor, easy-to-reach leak can take about three hours, and a large or hard-to-reach one up to three days. Replacing flooring or cabinets afterward can add several weeks. [6]
