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How to find a water leak

We'll help you locate the leak using the meter, toilets, and common leak spots.

How-to · Home plumbing
30–60 min
What you'll need
  • Flashlight
  • Food coloring (for toilet test)
  • Paper and pen (to record meter readings)

At a glance

  • Read the water meter with all fixtures off—if it moves, you have a leak somewhere in the system.
  • Check toilets first: add food coloring to the tank; color in the bowl within 5 minutes means a leaking flapper.
  • Listen at walls and floors for hissing or dripping; feel for damp spots or soft drywall.
  • Inspect under sinks, behind toilets, and at the water heater for wet spots or corrosion.
  • Call a plumber if the meter moves but you cannot find the leak—it may be under the slab or in the main line.
Quick triage — pick your path

Get started

Choose the option that matches what you see. You can jump straight to that section.

Steps

Goal: Confirm a leak exists and narrow down its location.

  • Shut off all fixtures and appliances. Read the water meter. Wait 15 minutes.
  • Good: Meter reading is stable—no leak. Bad: Meter moved—you have a leak. Proceed to Check toilets.

Check toilets

Goal: Rule out toilet leaks—the most common hidden leak.

  • Add food coloring to each tank. Wait 5 minutes. Look in the bowls.
  • Good: No color in any bowl—toilets are fine. Proceed to Inspect fixtures.
  • Bad: Color in a bowl—that toilet’s flapper is leaking. Replace the flapper.

Inspect fixtures

Goal: Find visible leaks at sinks, toilets, and the water heater.

  • Look under sinks, behind toilets, at the water heater. Feel for dampness. Listen for hissing.
  • Good: You find the leak. Fix it or call a plumber. Proceed to Verification.
  • Bad: No visible leak but meter still moves—proceed to Listen and check slab.

Listen and check slab

Goal: Find leaks in walls or under the slab.

  • Listen at walls for hissing or dripping. Check for warm spots on the floor or unexplained moisture.
  • Good: You locate the leak. Call a plumber for repair. Proceed to Verification.
  • Bad: Cannot find it—call a plumber with leak detection equipment.

When to get help

Call a plumber if:

  • The meter moves but you cannot find the leak.
  • You see signs of a slab or main-line leak (warm floor, persistent moisture).
  • The leak is behind a wall or under the foundation.

Verification

  • Meter reading is stable after fixing the leak (wait 15 minutes with all fixtures off).
  • No food coloring in toilet bowls.
  • No drips, puddles, or damp spots at fixtures.

Reviewed by Blackbox Atlas

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