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Using your water meter to find a hidden leak

Two local water utilities and the EPA describe the same meter test.

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Mon–Sat · Monterey Park, Alhambra, Rosemead, San Gabriel and nearby

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Updated · 3 min read

Straight answer

In San Gabriel Valley homes: Turn off every tap and appliance, then watch the meter. The City of Alhambra's report says check after 15 minutes, and the EPA says check before and after two hours. If the meter moves, there is a leak somewhere on your side.

What this covers
  1. The test
  2. Separate the toilets
  3. If the meter still moves
  4. What happens next
  5. FAQs

The test

The City of Alhambra's water report puts it in one line: turn off all taps and water-using appliances, check the meter after 15 minutes, and if it moved you have a leak. The EPA's Fix a Leak Week page uses a longer window: read the meter before and after a two-hour period when no water is being used, and if it changes at all you probably have a leak.

Turn everything off then Read the meter then Wait then Read again1Turn everything off2Read the meter3Wait4Read again
The meter test in four steps.

Separate the toilets

Toilets are the usual hidden source. The EPA says to put a few drops of food coloring in the tank. If any color reaches the bowl after 10 minutes, you have a leak. Flush right after the test so the dye does not stain the tank.

Alhambra's report puts numbers on it: a toilet can lose up to 100 gallons a day from an invisible leak, and fixing it saves more than 30,000 gallons a year. A dripping tap can lose 15 to 20 gallons a day.

Invisible toilet leak: 100 gallons per day, from Alhambra's report, Dripping tap, upper: 20 gallons per day, from Alhambra's report, Dripping tap, lower: 15 gallons per day, from Alhambra's reportInvisible toilet leak100 gallons per day, from Alhambra's reportDripping tap, upper20 gallons per day, from Alhambra's reportDripping tap, lower15 gallons per day, from Alhambra's report
Per-day losses listed in the City of Alhambra's report.

Getting help in San Gabriel Valley

Small leaks under sinks are easy to miss in San Gabriel Valley homes. Details on leak repair are one click away, and you can send a message or text (310) 628-9399 at any time.

If the meter still moves

If the toilets pass and the meter still moves with everything off, the leak is probably in a supply line, an irrigation line or under the slab. Check outdoors first, then call.

What happens next

We shut off the water to isolated parts of the house to narrow down which section is leaking, then locate the leak with a listening device and repair or reroute that run.

FAQs

Does a moving meter always mean a leak?

It means water is moving through the meter. If nothing in the house should be using water, a leak is the likely reason.

Which test window should I use?

Either works as a start. Use the 15-minute check as a quick screen, and the two-hour check if the first one is unclear.

Does the meter show a leak on the city side?

The meter test covers the pipe on your side after the meter.

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