Turn off every faucet, toilet, and appliance that uses water. Then go look at your water meter. If the dial or the small triangle on the face is moving, you have a leak somewhere in the system. That’s the whole test, and this article walks through exactly how to do it, what you’re looking at, and what to do next.
Find Your Water Meter
The meter is usually at the front of the property, flush with the ground inside a concrete or plastic box marked “Water.” Lift the lid, brush away any dirt or spiderwebs, and look at the face of the meter.
Most residential meters have two things to watch: a sweep hand (like a clock hand) that rotates as water flows, and a small leak indicator, typically a triangle or star-shaped dial that’s more sensitive than the main hand. On older meters it might be a small red, blue, or silver triangle. On digital meters, look for a flow indicator light or a decimal display that keeps ticking.
Run the Test
- Make sure no water is running in the house. Check dishwashers, washing machines, ice makers, and irrigation controllers. Turn them off or put them in a paused state.
- Do not flush any toilets and don’t run a tap for the duration of the test.
- Watch the leak indicator for 10 to 15 minutes without using any water. If it moves even slightly, water is flowing through the meter.
- For a slower leak, read the meter’s main register (the row of numbers), write it down, wait 30 to 60 minutes with no water use, and read it again. Any increase confirms flow.
A test that shows zero movement means no detectable leak at the point where the main supply enters your property. That doesn’t rule out a slow drip inside the house, but it does tell you the meter isn’t catching anything meaningful right now.
Isolate the Leak: Inside vs. Outside
Once you confirm the meter is moving, the next step is figuring out whether the leak is between the meter and the house (the service line) or inside the house itself.
Find the main shut-off valve. In homes with a basement or crawl space, it’s typically near the front foundation wall where the supply pipe enters. In slab-foundation homes (common in California), it may be near the water heater or under the kitchen sink. Close it fully. Go back to the meter. If the indicator is still moving after the valve is closed, the leak is in the underground service line between the meter and the house. That’s a serious situation requiring a licensed plumber, not a homeowner fix.
If the indicator stops moving when the main valve is closed, the leak is somewhere inside the house. A licensed plumber can pinpoint it faster with pressure testing equipment than you can by checking room by room.
Common Sources When the Meter Confirms a Leak
This section helps you gather information before calling a plumber, not fix things yourself.
Toilets are the most frequent culprit. A flapper that doesn’t seat correctly lets water run continuously from the tank into the bowl. You often won’t hear it. Drop a few drops of food coloring in the tank, wait 15 to 30 minutes without flushing, and check the bowl. Color in the bowl means it’s leaking through. Tell your plumber which toilet tested positive.
Supply lines and shut-off valves under sinks and behind toilets crack over time, especially braided stainless lines that are 10 or more years old. Check visually for moisture, mineral staining, or a slow drip. That’s useful info to hand off when you call.
Irrigation systems leak underground or at heads that stick open. If you have an irrigation zone, close its shut-off and re-run the meter test to see if that stops the indicator. If it does, the plumber (or your irrigation contractor) knows where to start.
The service line from meter to house is usually polyethylene or copper. Tree roots, soil movement, and corrosion can cause pinhole leaks or full breaks. A constantly running meter after the main valve is shut off almost always means a service line problem. This requires excavation and permits in most jurisdictions.
Water heaters can develop slow leaks at the temperature and pressure relief valve or at connections. Look for corrosion or pooled water around the base.
What the Moving Dial Actually Tells You
A moving indicator with nothing running inside the house is not ambiguous. Water is leaving the system somewhere. The meter doesn’t lie.
What it doesn’t tell you is where the leak is, how serious it is, or whether it’s a quick fix or an excavation job. A slow service line leak might only show as a barely perceptible movement of the triangle. A broken irrigation line might spin the sweep hand visibly. Both need attention, just at different urgencies.
If your water bill spiked, compare the current meter reading to what the utility shows on your last bill and roughly calculate the daily usage. A running toilet can lose 200 gallons or more per day. A service line break can run thousands of gallons before anyone notices.
When to Call a Licensed Plumber
Call a licensed plumber if:
- The meter keeps moving after you’ve closed the main shut-off valve (service line leak)
- You can’t find the source inside despite a confirmed positive test
- The meter reading shows unusually high consumption with no obvious interior cause
- You see wet spots in the yard with no irrigation explanation
- The meter test is positive and the property has older galvanized or polybutylene pipe
Diagnosing and repairing supply lines, especially anything underground, requires pressure testing equipment, locating tools, and permits in most jurisdictions. It’s not a homeowner repair.
When hiring someone, verify their license at cslb.ca.gov before any work begins. In California, plumbing work on a residence generally requires a C-36 licensed contractor. Ask for the license number and check it yourself.
The meter test takes 15 minutes and costs nothing. It confirms whether a leak exists and helps you describe the problem accurately when you call a licensed plumber. That’s exactly what it’s for.