Why start at the meter
Before anyone listens to pipes or scans a floor, the first question is simple: is water actually leaving the system when nothing is turned on? The meter answers that without tools. In Fullerton, the city runs its own water utility, and the meter that feeds your bill usually sits in a concrete box near the street or sidewalk.
A meter test does not tell you exactly where a leak is. It tells you whether there is one, and with two or three valve changes it tells you which part of the plumbing to suspect. That narrows the search and gives a plumber a head start.
Before you lift the lid
A false result usually comes from something still using water. Shut all of these off first.
- Every faucet, inside and outside, including hose bibs.
- Dishwasher, washing machine and any running cycle.
- Refrigerator ice maker and water dispenser, or close its supply valve.
- Irrigation controller set to off, not just paused.
- Water softener or filter in regeneration or backflush mode.
- Toilets: wait until every tank has finished refilling.
- Evaporative cooler, pool auto-fill or fountain if you have one.
How to run the test
- Open the meter box carefully.Use a screwdriver or meter key to lift the lid. Watch for spiders, wasps and standing water. Do not remove or adjust anything inside the box.
- Find the low-flow indicator.Many meters have a small triangle, star or gear-shaped dial that spins with even a trickle of flow. Digital meters may show a flow symbol or rate instead.
- Write down the reading.Note the full number and the time. Take a photo so you have a record if you later talk to the city or an insurer.
- Wait without using water.Give it 15 to 30 minutes. For a very slow leak, read it before bed and again in the morning with nothing used overnight.
- Read it again.Any change in the number, or a moving low-flow indicator, means water is passing the meter somewhere.
Narrowing it down with valves
If the meter moved, use these follow-up checks one at a time and watch the indicator after each.
- IfThe indicator keeps moving after you close the main house shutoffThe leak is likely outside, on the service line between the meter and the house or on an irrigation line. See the service line and sprinkler guides.
- IfIt stops when the house shutoff is closedThe leak is inside the house plumbing. Reopen the shutoff and continue to the next check.
- IfIt stops when the cold inlet on top of the water heater is closedThe leak is probably on a hot water line, which in slab homes often runs under the floor.
- IfIt stops only when toilet supply valves are closedA toilet is leaking internally. Do a dye test before suspecting pipes.
What to note for a plumber
- Readings
- Start and end numbers with times
- Indicator
- Moving, still, or moving only sometimes
- Valve checks
- Which shutoff stopped the movement
- Clues
- Warm floors, sounds, damp spots, stains
- Bills
- The last several months of usage
Common questions
How long should I wait between meter readings?
Fifteen to thirty minutes is usually enough to see a moderate leak. For a very slow one, compare a bedtime reading with a morning reading after no water use overnight.
My meter does not have a low-flow indicator. Can I still test?
Yes. Compare the full reading over a longer quiet period, such as overnight. Any increase with nothing running suggests a leak.
Is it safe to open the meter box?
Lifting the lid to read the meter is generally fine, but do not tamper with the meter or the city's valve. If the lid is stuck or damaged, contact the city's water utility.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.