Start with the water meter test
The meter tells you whether water is leaving the system when nothing should be running. EPA's WaterSense program describes the simplest version: check the meter before and after a two-hour period when no water is used. If the reading changes, there is almost certainly a leak.
- Turn off every faucet and appliance, and make sure no toilet is refilling or irrigation is running.
- Read the meter, or watch its small leak-indicator dial, which spins with even a slow drip.
- Wait two hours without using water, then read it again.
- If it moved, close the main shutoff inside the house and repeat. Movement with the house valve closed means the leak is underground, on the service line.
How to find a water leak in your house, room by room
Before anyone opens a wall, rule out the leaks you can find yourself. Toilets are the usual suspect: EPA suggests a few drops of food coloring in the tank; if the color shows up in the bowl without a flush, the flapper or flush valve is leaking. Then check faucets and showerheads for drips, the water heater's relief valve pipe, the supply lines under sinks and behind the washer, the refrigerator's ice maker line and the irrigation system.
The methods plumbers use
| Method | What it finds | Limits |
|---|---|---|
| Isolation and pressure testing | Which line leaks: hot or cold, one branch or another | Shows the line, not the spot |
| Acoustic listening | The hiss of water escaping a pressurized pipe, through floors and soil | Harder with background noise, deep pipe or plastic pipe |
| Thermal imaging | Warm spots from a hot-water leak, cool damp areas from a cold one | Sees surfaces, not pipes deep in a slab |
| Tracer gas | A hydrogen and nitrogen mix pushed into a drained line, detected where it escapes | Slower; used when acoustic methods fail |
| Moisture meter | Damp drywall, flooring and framing | Shows where water went, not always where it came from |
| Pipe locator | The route and depth of a buried line | Locates the pipe, not the leak |
Inside a wall, under a slab or in the yard
A leak inside a wall usually announces itself with a stain, soft drywall, peeling paint or a musty smell near a bathroom or kitchen wall. A leak under a slab shows up as a warm spot on the floor, the sound of running water with every fixture off, or a water heater that runs constantly; our slab leak repair page covers that case in detail. A leak in the yard, between the meter and the house, leaves a soft or unusually green strip of lawn and a meter that moves with the house valve closed; see water line repair.
How much water a small leak wastes
Slow leaks feel harmless because they're quiet. EPA's figures show how they add up.
| EPA WaterSense figure | Amount |
|---|---|
| Water an average family can waste to household leaks, per week | 180 gallons |
| Same, per year | 9,400 gallons |
| Share of homes with leaks wasting 50 gallons or more a day | 9 percent |
| A faucet dripping once per second, per year | over 3,000 gallons |
| Household leaks nationwide, per year | nearly 1 trillion gallons |
Source: U.S. EPA WaterSense, Statistics and Facts (updated March 11, 2026) and Fix a Leak Week (updated March 13, 2026).
What detection costs, and what it doesn't include
Fixr's May 2025 guide puts locating a slab leak at $100 to $400, depending on how invasive the search has to be. That buys a located leak, not a repaired one: the repair is quoted separately once the plumber knows where the leak is and what it's in. Ask whether the detection fee is credited toward the repair if the same company does both, and whether the report includes the method used and a marked location.
Leak and pipe guides
- Slab leak repair
Spot repair through the floor versus rerouting the line overhead.
- Pinhole leak in copper pipe
Why copper pits from the inside and when patching stops working.
- Repipe cost
Whole-house PEX or copper, galvanized and polybutylene replacement.
- Water line repair
The service line from the meter to the house, and who pays for it.
- Low water pressure
Pressure regulators, clogged aerators, galvanized pipe and hidden leaks.
Hidden leak questions
Will my water utility find the leak for me?
Utilities often flag unusual usage on a bill and some will check the meter, but finding a leak on your side of the meter is the owner’s job. Ask whether the utility offers a leak adjustment on the bill once the repair is done.
Can the meter show a leak when nothing in the house is wet?
Yes. If the meter moves with the house’s main shutoff closed, the leak is on the service line between the meter and the house, underground. That is a different repair, covered on our water line page.
How precisely can a plumber locate a leak?
With acoustic equipment on a pressurized line, a skilled technician can usually narrow a leak to a small area, so the opening in the floor or wall stays small. Background noise, pipe material and depth all affect it.
Does homeowners insurance pay for finding a leak?
Some policies pay to access and locate a leak once damage from it is covered; many don’t. Read the policy’s wording on tear-out and access before you book.
Sources
- WaterSense Statistics and Facts, U.S. Environmental Protection Agency, updated March 11, 2026.
- Fix a Leak Week, U.S. Environmental Protection Agency, updated March 13, 2026.
- Slab Leak Repair Cost, Fixr, updated May 1, 2025.
Reviewed September 27, 2026. Found an error? Write to admin@plumbingrepairquotes.com.