Plumbing guide · Green Valley, AZ

How to Find a Water Leak in Your House

To find a water leak in your house, turn everything off and watch the water meter: if it moves, a leak exists. Then check toilets, taps, supply lines, the heater and the yard in that order, and call a plumber in Green Valley, AZ when the source is hidden.

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Water heater1Sinks, toilets, showers2Water line under the slab3Main drain4Sewer line and cleanout5
  1. Run the meter testAll water off, read the meter, wait an hour, read again.
  2. Check the usual suspectsToilets, taps, supply lines and the heater pan, with a dry paper towel.
  3. Call when the leak is hiddenInside a wall, under a slab or under the yard needs listening gear.
The short answer

How to find a water leak in your house: the short version

The order matters. Confirm the leak first, check the simple fixtures second, and bring in equipment only for what you cannot see.

At a glance
  • Start with the meterA dial that moves with all water off proves a leak exists.
  • Test the toilets with food coloringColor in the bowl after fifteen minutes means a leaking flapper.
  • Check under sinks with a dry towelPress it on every nut and valve, then look for a damp patch.
  • Walk the yardIrrigation valves, hose bibs, pool fill and the cooler float are common leaks.
  • Listen and feel for slab cluesA warm floor patch or a faint hiss at night points below.
  • Call for hidden leaksListening gear and thermal imaging find the spot without opening walls.
Step one

How to find a water leak in your house, starting with the meter

One test tells you whether a leak exists before you open a wall.

A leak is easier to find when you stop guessing and start eliminating. This section sets up the one test that tells you whether a leak exists at all, before you open a single wall.

How do I know if the house has a hidden leak?

Use the water meter as a witness. Make sure every tap, appliance and irrigation zone is off, and that nobody is running the dishwasher, the washer or the ice maker. Then go to the meter and look at the small dial or triangle that spins at low flow. If it moves with everything off, water is leaving the pipes somewhere.

For a number to compare, write down the meter reading, wait an hour with no water used, and read it again. Any change means a leak. The meter and its box belong to your water provider, so lift the lid gently, do not touch the shutoff or the seals, and put it back as you found it. Which provider serves your address depends on where you live in Green Valley; the name is on your bill.

The meter test

  1. Everything off

    Taps closed, appliances idle, irrigation paused, no one flushing.

  2. Read the meter

    Note the dial or the digits, or take a photo with the date.

  3. Wait an hour

    Stay out of the water. Do not run the heater or the cooler.

  4. Read again

    Any change, or a moving dial, points to a leak.

What are the quieter signs of a leak?

A higher bill with no change in habits is the most common clue. A Green Valley water district’s FAQ lists a leaking toilet or faucet that is hard to detect as a likely reason for a high bill, which is true of any house. Other signs are low pressure, the sound of water when everything is off, warm spots on a floor, a musty smell in a closet and paint that bubbles low on a wall.

Clues
SignWhat it can point to
Meter moves with all water offA leak somewhere between the meter and the fixtures
Sound of running water at nightA running toilet, or a pressurized line leaking
Warm patch on a slab floorA leak in a hot-water line under the floor
Bubbling paint or stained drywallA slow leak in the wall behind it
Musty smell in a cabinet or closetA slow leak at a trap, supply line or heater
Falling pressureA leak, a failing valve or a clogged line
Signs inside the house.
Step two

Fixture by fixture: the leaks you can find yourself

Toilets, taps and supply lines cause most small losses.

Walk the house in the same order every time. Start with the fixtures that fail most often, then move to the ones that hide.

Where do leaks start inside the house?

Most hidden water losses come from a short list. Toilets lose water silently around the flapper. Faucets drip into the drain where you cannot see them. Supply lines under sinks sweat, weep or split at the nut. Water heaters leak from the relief valve or the fittings. Shower arms and tub spouts leak into the wall.

Check each one with a dry paper towel. A damp towel under a supply line tells you more than a long look. Press it against the nut, the valve and the pipe and see where the color changes. A flashlight on the underside of a vanity often finds the culprit in a minute.

Fixture checks
FixtureQuick testLikely cause
ToiletTint the tank water, wait fifteen minutes, check the bowlWorn flapper or fill valve
FaucetDry the base and spout with a towel, check after an hourCartridge, washer or O-ring
Under-sink supply linesPress a dry paper towel on each nutLoose nut or cracked line
Water heaterCheck the pan and the relief valve pipeValve, fitting or tank
Shower and tubRun the water, then look at the ceiling below or the wall behindValve body, arm or tile seal
Washer hosesLook behind the machine with a flashlightBrittle hose or loose coupling
A towel test for each fixture.

How do I do the toilet dye test properly?

Lift the tank lid and drop in a few drops of food coloring. Do not flush. Wait fifteen to twenty minutes and look at the bowl. If color appears, the flapper is letting water through, even when the toilet seems quiet. Flush to clear the dye before it stains.

A toilet can lose a surprising amount of water a day this way, and the fix is inexpensive. If the flapper looks fine, check the fill valve and the overflow tube. The page for toilet repair describes the parts, and the faucet repair page explains the same checks for taps.

Dye test
Color in the bowl without a flush means water is slipping past the flapper.
Step three

Yard, irrigation and equipment leaks in a desert home

Water outside the house counts on the meter too.

A desert yard adds leak sources that a cooler-climate house does not have. Check them before you assume the problem is in the walls.

Could the leak be outdoors?

Walk the lot with the irrigation off and look at the ground. A wet patch that stays after days of dry weather, or a green strip in an otherwise dry yard, is a sign. Listen near the valve box and the backflow device. A hiss with the system off points to a failed valve or a split pipe. Look at the pool auto-fill and the evaporative cooler’s float valve; both can run all day.

The line between the meter and the house is a favorite hiding place. Caliche and rocky soil can stress a buried pipe at the joints, and a leak there may show only as a damp spot or a dip in the ground. If you suspect it, the water line repair page explains what the repair involves. Call 811 (Arizona 811, Blue Stake) before anyone digs.

Outdoor checks
  • Irrigation valvesRun each zone and look for a geyser or a pool at the valve box
  • Backflow assemblyListen for a hiss when the system is off
  • Hose bibsA drip at the stem is a leak, even if the hose is off
  • Pool auto-fillA float valve stuck open can run for days
  • Evaporative coolerCheck the float and the overflow line
  • Buried supplyLook for a damp strip between the meter and the wall

What about the softener, the heater and the cooler?

Equipment that uses water on a schedule can leak on a schedule. A softener that regenerates at night can drain onto the floor if its drain line is loose. A heater with a failing relief valve may weep only during a heating cycle. A roof-mounted cooler can overflow after a storm. If the leak seems to come and go, note the time of day and compare it with the appliance’s cycle.

A water heater leak is never a cosmetic problem. A dry pan today can fill tomorrow. The water heater repair page lists the common faults and what each one means.

Timed leaks
A leak that keeps a schedule usually belongs to a machine on a schedule.
Hidden leaks

Finding a water leak in a slab, wall or attic

Clues that point to a leak you cannot see.

The worst leaks are the ones you cannot see. In slab-on-grade homes, much of the plumbing runs in the floor or in the attic, which makes those leaks hard to reach and easy to miss.

How do I tell if the leak is under the slab?

A slab leak often announces itself with sound, a warm spot, a rising bill and low pressure. Walk barefoot across the floor and feel for a patch that is warmer than the rest. Listen along walls and floors at night for a trickle. Look for cracks in grout or baseboards that appeared recently. These signs on their own do not prove it, but together they are strong.

Older homes can have pipe that has worn thin in places, and a pinhole can sit in the same spot for years before it sprays. A plumber can find the leak without breaking the floor by using listening gear and thermal imaging. For the full list of signs, read signs of a slab leak, and for how the work is done see slab leak repair.

Slab clues
A warm patch or a hiss through the floor often points to a hot-water line under the slab.

What about leaks in the attic or above a ceiling?

Attic pipes can be stressed by summer heat and, in rare cold spells, by freezing. A stain on a ceiling that spreads after the heater runs, or that appears on a dry day, can be a pipe in the attic or a heater drain line. If it is bulging, keep people out from under it, switch off power to lights nearby and call. Do not poke it.

Remember that stains also come from the roof. After a monsoon downpour a ceiling mark that matches the storm is more likely roof water than plumbing. A stain that returns on dry weeks is a plumbing suspect.

Ceiling stains
Where the stain isAppears whenLikelier source
Under a bathroomAfter showersShower valve, drain or tub seal
Under the heater closetAfter the heater cyclesHeater fitting, relief line or tank
Along an exterior wallAfter heavy rainRoof or window, not plumbing
In the middle of a ceilingOn dry days tooSupply or drain line above
Below a roof coolerAfter the cooler runsCooler line or overflow
Timing separates plumbing from roof water.
What next

What to do once you find a water leak in your house

A short sequence protects the house while you decide.

Once you have found a leak, or confirmed that one exists, these are the next moves. Doing them in order protects the house.

  1. Close the valve closest to the leak

    A fixture has its own shutoff valve under it. Turn it clockwise until it stops. If no valve exists, close the main valve; the main valve guide shows how.

  2. Protect what is wet

    Move rugs and boxes, soak up standing water with towels and run a fan. Open cabinet doors so the space can dry.

  3. Turn off the heater if it is involved

    If the leak is on the hot side or near the heater, switch off the breaker or the gas control. Never run a heater dry.

  4. Take photos and notes

    Record the meter reading, the location and what you did. A clear record helps the plumber and your insurance paperwork.

  5. Call about a hidden leak

    If the meter test says a leak exists and you cannot find it, call. A plumber with listening gear finds it without cutting walls first.

When is the leak a job for a professional tool?

A hidden line leak, a leak inside a wall, a leak in the slab and a leak in a buried pipe all need equipment. Acoustic listening gear picks up the sound a pressurized leak makes. A thermal camera shows warm patches. A tracer gas test traces the source without digging. The leak detection page describes these methods in more detail.

Detection comes before repair, so that the repair is small. A repair done on a guess often means a bigger hole than needed. If the leak is on the supply side, see water line repair and pipe repair for what comes after the tracing.

Tools that find hidden leaks
Detection finds the spot so the repair can be small.
When to call

Leak signs that call for equipment

A towel and a flashlight stop helping at this point.

  1. The meter moves and you cannot find why

    A leak is hiding in a wall, slab or buried line.

  2. Water is spreading in a ceiling or wall

    Close the main valve and call. The sooner it stops, the smaller the repair.

  3. A warm floor patch or a sound under the slab

    Hot-water lines under a slab need detection gear.

  4. A wet spot in the yard with no sprinkler on

    The line to the house may be leaking underground.

Related services

Services when you need help to find a water leak

Leak detection

Tracing a hidden leak without opening walls.

Leak detection details →

Slab leak repair

Repair of lines under the floor.

Slab leak repair details →

Water line repair

Fixing the pipe between the meter and the house.

Water line repair details →

Burst pipe repair

Stopping a line that has split.

Burst pipe repair details →
Questions

Questions about finding a leak

Can I learn how to find a water leak in your house on my own, without a plumber?
Turn off all water, read the meter, wait an hour and read it again. If it moved, check the toilets with food coloring, press a dry paper towel on each supply line and walk the yard. In Green Valley, AZ, irrigation and the cooler float are frequent culprits.
How do I read the meter to check for a leak?
Lift the lid carefully and look for the low-flow dial or triangle. With every tap and appliance off, it should be still. Write down the reading, wait an hour and compare. Your Green Valley water provider owns the meter, so do not touch the shutoff or the seals.
Why is my water bill high when I use the same amount?
A hidden leak is the usual cause, often a toilet flapper, a dripping tap or a buried line. A Green Valley water district’s FAQ points to leaky toilets and faucets as likely reasons for a high bill. Do the meter test, then check fixtures one at a time.
How long does it take to find a hidden leak?
A fixture check takes minutes, and the meter test takes an hour. A hidden line leak is quicker to find with listening gear than by opening walls. In Green Valley, a plumber can trace many leaks in a single visit. Pricing is easy to ask about on the call.
Can a leak be under the slab of my home?
Yes. Many Green Valley homes are built on slabs, and some lines run in or under them. Warm patches, a hiss at night, a rising bill and falling pressure are clues. Older homes are more likely to have thin or worn pipes.
What does a toilet leak look like?
Often nothing. The tank refills now and then with no one flushing, or you hear a hiss. A few drops of food coloring in the tank show it: if color reaches the bowl without a flush, the flapper is leaking. It is a common, simple fix.
Is a wet spot in my yard a leak?
It can be, if the ground stays damp when the sprinklers are off. In Green Valley, AZ, a green strip in dry soil or a hiss at the valve box are clues. Shut the irrigation, run the meter test and call before anyone digs. Call 811 first.
How do I find a leak behind a wall?
Look for bubbling paint, stains, a musty smell and a warm wall. Run the meter test to confirm. A plumber uses acoustic gear and thermal imaging to find the spot, so the opening in the wall is small. Do not cut drywall on a guess.
What should I do the moment I find a leak?
Shut the valve nearest the leak or the main, clear belongings, cut power to the heater if it is near and photograph the damage. Then call. In Green Valley, AZ, the line is staffed around the clock and a same-day visit can be arranged.
Will a leak damage my house if I wait?
Yes. Water that sits behind walls and under floors damages drywall, framing and flooring, and it can start mold. A small leak in a Green Valley home grows with time. Fix it early, and call if you cannot find the source.
More guides

More guides for Green Valley homeowners

Leak you cannot find?

Call and say what the meter is doing. Someone picks up at any hour, and a same-day visit is possible.

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