Pipes & water supply

Water meter reading high, suspect hidden leak

An unexplained jump in your water bill or meter reading, with no obvious dripping fixture, usually means a hidden leak somewhere in the supply line or a running toilet.

Difficulty
Easy
Time
1–3 hours (diagnosis)
DIY cost
$5–$15
Pro cost
$200–$800+ (leak detection and repair)

Symptoms

  • Water bill noticeably higher than usual with no change in habits
  • Meter dial moves even with everything in the house turned off
  • No visible wet spots or dripping fixtures found so far
  • Possibly a damp spot in the yard

Likely causes

  • CommonRunning or slowly leaking toilet flapperA worn flapper can let water silently trickle from the tank into the bowl continuously, which is the single most common hidden water waster.
  • CommonUnderground leak in the service line between the meter and the houseA crack in the buried supply line can leak into the ground with no visible sign indoors.
  • PossibleLeak inside a wall or under a slabA pipe leaking within a concealed space may not show visible water for a long time.
  • PossibleLeaking irrigation system or outdoor fixtureA cracked sprinkler line or leaking hose bib can run for a long time before being noticed.

What to do

  1. Turn off every fixture and appliance that uses water in the house, and don't use any water for a couple of hours.
  2. Find your water meter and note the reading, then check it again after the no-use period; any movement means an active leak.
  3. Check every toilet by putting a few drops of food coloring in the tank and waiting 10–15 minutes without flushing; color in the bowl means the flapper is leaking.
  4. Inspect the yard for unusually wet or lush patches, especially between the meter and the house, which can indicate an underground leak.
  5. Check outdoor irrigation zones and hose bibs for any dripping or unexplained wet ground.
  6. If the meter moves with everything off and no toilet or outdoor leak is found, the leak is likely inside a wall or under the slab and needs a plumber's leak detection equipment.
  7. Keep a record of readings and dates to share with a plumber, which helps them estimate leak severity and location.

Tools and parts

  • Food coloring
  • Flashlight (for meter reading)
Toilet flapper (if that's the cause)Search: “universal toilet flapper replacement”

When to call a pro

Call a plumber with leak detection equipment if the meter shows movement but you can't find any visible source after checking toilets and the yard.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.