Leak Detection Services

Reviewed 2026-07-30

Leak detection finds hidden water leaks inside walls, under slabs, or underground. These leaks cause high water bills, damp spots, or water loss with no visible source.

Symptoms leak detection solves

A water bill that's significantly higher with no change in usage habits
The water meter continues to run when every fixture in the house is off
A warm or damp spot on the floor, especially over a slab foundation
The sound of running water when no fixture is in use
A musty smell or mold appearing on a wall with no obvious external water source
Low water pressure at one or more fixtures with no other explanation
Visible water pooling in the yard over a suspected supply or irrigation line

When to book leak detection

As soon as a water bill spikes unexpectedly compared to prior months
If the water meter's leak indicator dial moves while all fixtures are off
When a damp or warm spot appears on flooring with no visible plumbing nearby
Before finishing a basement slab, to rule out a slab leak first

What happens during leak detection

Technician checks the water meter with all fixtures off to confirm a leak exists and estimate its severity
Isolation testing narrows the leak to a zone: main line, a specific fixture line, or the slab
Acoustic listening equipment amplifies the sound of water escaping under pressure to pinpoint the location
For slab leaks, thermal imaging can detect a heat signature from a hot water line leaking beneath the floor
Video pipe inspection may be used for accessible sections to visually confirm a crack or failed fitting
Once located, the exact repair point is marked, minimizing the amount of wall, floor, or slab that needs to be opened

Leak Detection methods and approaches

Acoustic leak detection

Using sensitive listening equipment to amplify the sound of pressurized water escaping through a crack or joint, allowing technicians to pinpoint a leak without extensive excavation or demolition.

Thermal imaging

An infrared camera detects temperature differences on floors or walls caused by a leaking hot water line, useful for slab leaks that don't yet show visible moisture.

Pressure testing / isolation

Shutting off sections of the plumbing system one at a time while monitoring the water meter to isolate which zone or fixture line contains the leak.

What drives leak detection pricing

Basic leak detection service call: $150–$400
Acoustic or thermal imaging detection for a slab leak: $300–$600
Detection combined with repair access point marking: often bundled into detection fee
Complexity — leaks under concrete slabs or in multi-story walls cost more to isolate than an accessible crawl space pipe
House size and number of zones that need isolation testing
Whether the leak requires specialized equipment (ground microphones, tracer gas) versus standard acoustic tools

See the full cost guide →

Questions to ask your licensed plumber or leak detection specialist

What method will you use given where you suspect the leak is located?
Will the detection fee include marking the exact repair location to minimize demolition?
How confident are you in the location before any exploratory opening begins?
Is detection billed separately from the repair, or bundled together?
Do you also perform the repair, or will I need to hire a separate plumber?
What's your estimate for how much floor, wall, or slab will need to be opened?

Leak Detection safety and licensing

A slab leak on a hot water line left unaddressed can undermine the slab over time and should be treated as a priority repair, not just monitored.
Do not attempt to cut into a slab or wall yourself to search for a leak — professional detection avoids unnecessary demolition and structural risk.
If a leak is near an electrical panel or outlet, avoid contact with the area and have an electrician check for water intrusion before restoring power.

Leak Detection questions homeowners ask

How can I tell if I have a hidden leak?

Turn off every fixture and appliance that uses water, then check the water meter's leak indicator (a small triangle or dial) — if it moves, water is flowing somewhere in the system even though nothing is turned on.

How much water can a hidden leak waste?

The EPA estimates that household leaks can waste more than 10,000 gallons of water per year, and a running toilet alone can waste up to 200 gallons per day.

Is slab leak detection expensive?

Detection itself typically costs $300–$600 using acoustic or thermal methods, which is far less than the cost of exploratory demolition and often reveals the leak's exact location within a few feet.

Problems that lead to leak detection

Sources for this leak detection guide

EPA WaterSense, Fix a Leak Week Program Data
IAPMO Uniform Plumbing Code
InterNACHI, Plumbing Inspection Standards