Leak detection: what to know

What the job involves, what changes the price, and what to ask a pro.

What leak detection is

Leak detection finds where water or gas is escaping, often without opening walls. A pro uses pressure tests, listening gear and thermal or camera tools to pin down the spot before any repair starts.

Signs you need it

  • Your water bill rises with no change in use, which can mean a hidden leak
  • A warm spot on a tile or hardwood floor, especially over a slab or near the water heater
  • Damp or stained drywall, baseboards or a ceiling with no visible source
  • The water meter keeps turning when every fixture is off
  • A musty smell, bubbling paint or cupped flooring in one area of the house

What the pro does

  • Read the water meter with every fixture off, record the number, and check it again after a set period
  • Pressure test the supply and drain lines to confirm which system is losing water
  • Use listening gear or a ground microphone to narrow down the sound of escaping water
  • Use a thermal camera to find warm spots where hot water lines run under the floor
  • Run a camera down drain lines to find cracks, separated joints or root intrusion
  • Mark the location on the floor or a plan and describe the least damaging way to reach it

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Type of leak: supply, drain, slab or gas, since each needs different equipment
  • Whether the leak is under a slab or inside a wall with a finished surface
  • Size of the home and the number of lines that have to be checked
  • How many tests are needed to confirm the spot before any repair
  • Whether a camera is needed for a drain line or only pressure and listening
  • Whether a small test opening is needed to confirm the source

What a written quote should spell out

  • The test methods used and what each one found
  • The location of the leak, marked on a plan or described from a fixed landmark
  • Whether a camera or thermal scan is included, and the format of the report
  • Whether a repair is included in the same visit or quoted separately
  • Any opening needed for access, and who restores it

Questions to ask before you hire

  • Which tests will you run, and which one will confirm the source?
  • Can you give me a written report with the test results and the location?
  • If the leak is under the slab, what repair options are there, and what does each one involve?
  • Will you open anything to confirm the leak, and how large will the opening be?
  • Do you test the water heater and the supply line separately?
  • Can you provide photos and test results for an insurance claim?

Red flags

  • Pro who opens a floor or wall before running a test to confirm the leak
  • Pro who says he found a leak but cannot show the test that confirmed it
  • Pro who gives no written report with the location and method
  • Pro who recommends a full re-pipe without a test that shows it is needed

What you can do yourself

A homeowner can read the water meter with all fixtures off, record the reading, and check it again after an hour. Look for a running toilet or a dripping faucet as well. Stop there and call a pro for the actual location, since slabs and walls hide leaks, and cutting at the wrong spot creates new damage.

Licenses and permits

Leak detection and repair on water and drain systems is commonly licensed plumbing work, and gas leak testing may fall under a separate license or utility rules. Check with your state or local licensing agency for the rules where you live.

Leak detection questions

How can I tell whether a slab leak is under my house?

A warm spot on the floor, a meter that runs with the water off, or a sudden jump in the bill can all point to one. A pro confirms it with a pressure test and a thermal scan before any concrete is cut.

What is a meter test?

A meter test reads the water meter with every fixture off. If the reading or the leak indicator still moves, water is leaving the system somewhere, which starts the search.

Will leak detection open my walls?

It should not need to in most cases. A good pro finds the spot first and opens only what the repair requires.

What should I do if I smell gas?

Leave the house, do not use light switches or flames, and call the gas utility from outside. A gas leak is not a homeowner test job.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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