Plumbing guide · Green Valley, AZ
Signs of a Slab Leak
The signs of a slab leak are a spinning water meter while the house is idle, a patch of floor that stays warm, a hiss at night and a bill that creeps up unexplained. A Green Valley, AZ plumber can confirm it with a pressure test.
(928) 900-0082- Read the meter while idleClose every tap, then watch the dial.
- Check the floor at dawnA warm spot after the house has cooled matters.
- Rule out look-alikesCoolers, irrigation, pools and toilets first.
The signs of a slab leak, in short
A slab leak hides under the floor, so you read it from the meter, the bill, the sound and the floor.
- A dial that keeps turning while the house is idleThe best clue you can check yourself.
- A warm spot on the floor in the morningA hot line leaking under the slab.
- A hiss or trickle once the house goes quietWater escaping under pressure.
- A bill that keeps rising for no reasonA leak runs around the clock.
- Damp carpet, cracked tile or swollen baseboardsMoisture rising through the floor.
- Rule out look-alikes, then callCoolers, sprinklers, pools and running toilets can fool you.
What a slab leak is, and why it hides
A buried pipe leaks where you cannot see.
Under the floor of many homes, supply pipes run in or beneath the concrete foundation. A slab leak is a break in one of them. Because the pipe is buried, nothing drips where you can see it. The water goes into the ground, into the concrete, or up through the floor, and the signs show up somewhere else.
Why a slab leak hides so well
Most Green Valley homes sit on a slab rather than over a crawl space or basement. In many of them, some or all of the hot and cold lines run below the floor or through the slab, and the plumber’s job is to reach them without wrecking the house. That is why the early signs are indirect: a bill, a sound, a warm patch, a smell.
Not every slab house has slab-embedded lines. Some run overhead through the attic, and some mix both. Older homes are more likely to have lines in or under the concrete. If you are unsure, ask a plumber to look at where the lines enter the house.
Slab leak versus slab-adjacent leak
Not every leak near the slab is a slab leak. Water from a wall, the attic or the heater can run down and collect on the floor, and from above it looks identical. The difference matters because the repair is different. A camera, a listening device or a pressure test sorts it out. The leak detection page explains how.
| Where the leak is | How it reaches you | How it differs |
|---|---|---|
| Under the slab | Seeps up through concrete or tile joints | Pressure test shows a drop with fixtures off |
| Inside a wall | Stains and damp drywall above the floor | Moisture follows the pipe route |
| In the attic | Ceiling stains below | Easier to reach and fix |
| At the water heater | Water in the pan or on the garage floor | Visible, source is the tank |
| In an irrigation or pool line | A wet yard or soft ground | Not part of the house plumbing |
Slab leak signs you can see, hear and feel
Several clues together beat any single one.
There is no single telltale. A slab leak is usually diagnosed from a handful of signs that point the same way. If two or three apply to you, a test is worth doing.
Slab leak signs you can see, hear and feel
Water that runs under pressure all day makes noise. Some people hear a faint hiss or a trickle when the house is silent and every tap is off. Others notice a floor that feels warm in a spot where there is no sun, a hot line leaking beneath tile. Carpet may feel damp in one patch or smell musty, and baseboards may swell.
In a desert home, warm tile on a hot afternoon can be a false lead. Test at night or in the morning, when the floor should be cool. A spot that is still warm after the house has cooled, or that matches the path of a hot-water pipe, deserves a closer look.
- A hiss or trickle with every tap offListen in the quiet of night
- A warm spot on the floorTest in the morning, when the floor should be cool
- Damp carpet or a musty smellIn one patch, with no source above
- Cracks in tile or grout linesThat follow a straight line
- Swollen baseboards or lifted flooringWood and laminate absorb moisture
- A water meter that moves with everything offThe best clue you can check yourself
- A high bill with no change in useSlow, steady loss adds up
Signs in the bill and the pressure
A slab leak runs around the clock. That shows up in two places: the water bill and the pressure at the tap. A bill that climbs for no reason, without a new pool, a guest or a change in watering, is worth checking. Your water provider’s own guidance points to hidden toilet and faucet leaks as common culprits, and says to look at the meter and the area around it.
Falling pressure at several fixtures is a different clue. A large leak steals pressure from the whole system. If the drop is at only one fixture, it is more likely a clogged aerator. The why is my water pressure low guide helps you tell the two apart.
| Clue | What it suggests | Next step |
|---|---|---|
| Bill rises, same habits | A hidden leak somewhere | Meter test |
| Dial turns while idle | A leak after the meter | Check toilets, then call |
| Pressure down at every tap | A large leak or a pressure problem | Look at the regulator and call |
| Pressure down at one tap | A local issue | Clean the aerator |
| Hot water slow to arrive | Possibly a hot-line leak | Call for a test |
The meter test: confirming slab leak signs yourself
Fifteen minutes, no tools.
You can run a meter test in about fifteen minutes with no tools. It does not locate the leak, but it tells you whether a leak exists after the meter, which is the question that comes first.
The meter test, step by step
Look for the meter in a ground-level box close to the curb or property line. Lift the lid carefully, watching for insects and debris. Look for a small triangle, star or wheel that spins when water is moving. That is the leak indicator.
Turn off every tap, the dishwasher, the washer, the ice maker and the softener’s regeneration if you have one. Make sure no one flushes. Then watch the indicator. If it keeps moving, water is leaking somewhere after the meter. The next question is where.
Shut off every use
Taps, appliances and irrigation timers.
Open the meter box
Mind spiders and loose lids.
Find the leak indicator
A small wheel, triangle or star.
Watch for a minute or two
A moving indicator means a leak.
Note the reading
Wait ten or fifteen minutes and read again.
Narrowing it down before you call
A running toilet is the most common false alarm. Drop food coloring into each toilet tank, leave it alone for fifteen minutes and look at the bowl; tinted water points to a worn flapper. Next close the shutoff at the house and read the meter again. A stopped indicator puts the leak inside the house, while a moving one puts it in the yard line.
To locate the house shutoff, read how to shut off your main water valve. For a wider hunt, try how to find a water leak in your house.
- Toilet dye testColor in the bowl means a flapper leak
- Close the house mainMeter stops: leak is inside the house
- Meter keeps movingLeak is in the yard line
- Check hose bibs and irrigationDrip lines, valves and timers
- Check the water heater panDampness around the base
Look-alikes: leaks that are not under the slab
Desert homes have their own false alarms.
Things that look like a slab leak and are not
Several desert-home habits can imitate a slab leak. An evaporative cooler that overflows can soak a floor. A sprinkler zone with a stuck valve can saturate soil beside the foundation. A pool autofill can mask a leak and raise the bill. A warm floor over a hot-water pipe may simply be a hot-water pipe doing its job.
Rule these out first. It costs nothing, and it may save an unnecessary test. Check the cooler, the sprinkler timer and the pool before assuming the slab.
| Look-alike | Why it looks like a slab leak | How to rule it out |
|---|---|---|
| Evaporative cooler overflow | Wet floor near the cooler | Check the float and the pan |
| Stuck irrigation valve | Soggy soil beside the house | Turn off the zones and recheck the meter |
| Pool autofill | High bill, no visible leak | Turn off the autofill and watch the meter |
| Running toilet | Meter moves, no wet spot | Dye test |
| Hot-water pipe under a tile floor | Warm spot | Check at night; follow the pipe route |
| Plumbing sweat on a cold pipe | Damp spot by a wall | Wipe it dry; see if it returns |
The things that make a floor warm
A floor can feel warm for innocent reasons: afternoon sun through a west window, a heater vent, radiant heat from a hot attic through a ceiling, or the hot-water line passing beneath tile. A true slab leak on a hot line produces a warm spot that stays warm at any hour and often marks the path of the pipe.
If the warm spot is steady and matches the route of a hot line, call. Do not drill, pry or pour anything into the floor yourself.
- Warm in the afternoon onlyLikely sun or heat gain
- Warm at 6 a.m.Worth a test
- Warm along a straight lineFollows a pipe route
- Warm and dampCall right away
- Warm only above a ventThe vent, not the slab
Why lines under a slab fail
Corrosion, abrasion, movement and pressure.
Why lines under a slab fail
Pipes buried in concrete live in a harsh place. Concrete holds moisture against the metal, and soil minerals attack copper from outside while mineral-laden water attacks it from inside. Over the years the pipe wall thins until a pinhole opens. Hot lines expand and contract with every use, rubbing against the concrete and wearing a spot through.
Ground movement adds to it. Desert soil shrinks and swells with moisture, and rocky or caliche-bearing ground can press unevenly on a pipe. A pipe that rests on a hard stone can wear through where it touches. Water pressure that runs too high speeds every one of these processes.
| Cause | How it works | What helps |
|---|---|---|
| Outside corrosion | Soil minerals eat copper from the outside | Reroute the line out of the slab |
| Inside corrosion | Aggressive or mineral-heavy water thins the wall | Water treatment, a newer pipe |
| Abrasion | Hot pipe rubs the concrete as it expands | Sleeved or rerouted lines |
| Ground movement | Soil shifts and presses on the pipe | Careful bedding |
| High pressure | Constant stress at every weak spot | A working pressure regulator |
| Poor original work | Sharp bends, kinks, a stone beneath the pipe | Replace the affected run |
Pressure is a cause you can control
Near the main shutoff sits a pressure regulator, shaped a bit like a bell. With age it can stop doing its job and pass street pressure straight into the house, straining every pipe and fixture. An inexpensive gauge screwed onto a hose spigot reads the pressure in seconds.
Replacing a tired regulator costs far less than a repair under the floor. It is one of the few preventive steps that lowers the odds of a future slab leak. See the low water pressure page for the other end of the same problem.
What to do when you suspect a slab leak
Same day, without cutting the floor.
If you suspect a slab leak, act the same day. Water under the slab can soften soil, undermine concrete and ruin flooring. The earlier it is found, the smaller the repair.
What to do now
Shut the water at the main if you can find the signs of active leaking, such as a pool of water or a hissing sound. Run the meter test. Photograph the signs. Do not drill, chip or cut the floor yourself. Move rugs and valuables off the damp area, and open windows for air if the space is damp.
Then phone. Tell the plumber what you found: meter movement, warm spots, a high bill, sounds. They will arrive with equipment to listen to the pipe, check pressure and often use a thermal or electronic locator.
Shut off the main
If water is visibly escaping or you hear a hiss.
Run the meter test
Everything off, then watch the indicator.
Photograph the signs
Stains, cracks, meter readings, bills.
Protect the floor
Move rugs and furniture off damp areas.
Call a plumber
Describe what you found.
Do not cut the floor
Leave locating to the equipment.
How a plumber finds the exact spot
Locating a slab leak is detective work. A listening device catches the noise of water escaping beneath the concrete. A pressure test isolates the hot side from the cold side. A thermal camera can show a warm path. Tracer gas is another option for some jobs. The goal is to open the floor in one small spot, not a wide area.
- Pressure testIsolates hot and cold lines
- Acoustic listeningHears water escaping
- Thermal imagingShows a warm path
- Line tracingMaps the pipe route
- Small access openingOnly where the leak is
Repair routes and cleanup for a confirmed slab leak
From a small opening to a reroute.
Repair routes for a confirmed slab leak
There are three broad routes. A spot repair breaks through the slab at the leak and replaces that piece. A reroute abandons the leaking line and runs a new one through the walls or the attic. A repipe replaces the system. The right choice depends on how many leaks there have been, how the rest of the pipe tests and how much of the floor you are willing to open.
The slab leak repair page describes each route in detail. When a bigger step makes sense is covered in repiping a house: signs and cost. Price depends on the route, the access and the floor covering. Ask about pricing when you call.
| Route | What happens | Best when |
|---|---|---|
| Spot repair | Open the slab at the leak and replace the piece | One leak in otherwise sound lines |
| Reroute | Leaving the old line, running a new one overhead | Repeated leaks or hard access |
| Repipe | Replace the supply system | Failing material or many leaks |
| Pressure fix first | Replace a failing regulator | High pressure behind the leaks |
Cleanup after the leak
Water in a slab does damage after the leak is fixed. Wet insulation, flooring and baseboards must dry out completely, which takes airflow and time. Ask the plumber what drying you should do, and let your insurer know if you plan to file a claim. Read your own policy, since what is covered varies, and phone your insurer rather than assuming.
Mold follows moisture
Damp carpet and drywall can grow mold within days. Dry the area quickly, and discard soaked padding rather than hoping it will dry.
When slab leak signs mean it is time to call a plumber
Do not wait out any of these.
The dial turns while the house is idle
Water is escaping after the meter. Find out where.
A warm spot that stays warm at dawn
A hot line may be seeping under the slab.
Damp flooring with no visible source
Moisture rising through the slab.
A hiss in a silent house
Water under pressure is escaping somewhere.
Services for a suspected slab leak
These are the jobs that find and fix water lost under the floor.
Slab leak repair
Locating and repairing leaks under the foundation.
Slab leak repair details →Leak detection
Locating hidden water loss without opening walls.
Leak detection details →Water line repair
Leaks in the yard line to the house.
Water line repair details →Repiping
Replacing failing supply lines.
Repiping details →Questions about the signs of a slab leak
What are the first signs of a slab leak in a Green Valley home?
Can I find a slab leak with my water meter?
Why is part of my floor warm?
Will a slab leak always show on the floor?
How is a slab leak found without tearing up the floor?
What causes a slab leak?
Is a slab leak an emergency?
Do I need to repipe after a slab leak?
What decides the price of fixing a slab leak?
Could my high water bill be something else?
More guides for Green Valley homeowners
Suspect a leak under the floor? Call now.
Someone picks up whatever the hour. Describe what the meter, the floor and the bill are doing.