Short definition
The water meter leak test uses your utility’s water meter as a leak detector. Shut off every fixture, watch the meter or its leak-indicator dial, wait 15 minutes. Movement means water is flowing somewhere in the system. Then shut your building’s main valve and re-test to isolate whether the leak is inside or in the buried service line.
What it is
Every metered water service in Washington has a meter at the property line, usually in a concrete vault under the sidewalk strip — sometimes called a “buffalo box” or “curb stop.” The meter face has a main sweep dial and, on most modern meters, a small leak-indicator: a tiny triangle, star, or low-flow disc that spins on flow as small as 0.05 gallons per minute. That dial is more sensitive than the main reading.
The standard procedure:
- Turn off every water-using fixture, appliance, and irrigation valve.
- Disable auto-cycling appliances — ice maker, dishwasher, washing machine, water softener regen. (These can mimic a leak during the test.)
- Locate the meter.
- Note the reading and the position of the leak-indicator dial.
- Wait 15 minutes (1 hour for very slow leaks).
- Re-read.
Any movement = a leak somewhere downstream of the meter.
To isolate the side:
- Shut your building’s main shutoff (where the service line enters the house).
- Re-test the meter for another 15 minutes.
- Still moving = the leak is between the meter and the building shutoff — usually the buried service line, which most WA jurisdictions consider homeowner-owned.
- Stopped = the leak is inside. Continue with toilet dye tests, fixture inspection, and thermal/acoustic detection.
Why it matters to a homeowner
The meter is the only piece of plumbing in your house that can’t lie. Every gallon that flows through it is recorded. When you suspect a leak, the meter test takes 15 minutes and answers two questions that no amount of staring at fixtures will: is there a leak at all, and which side of the building shutoff is it on. Both answers shape what comes next — and what costs what.
If the meter test isolates the leak to the buried service line, that’s a different repair entirely. Service-line replacement in the Seattle area can run $3,000-$10,000 depending on length, depth, and street access. SPU and Tacoma Water both have programs and inspection options for this — but the bill is the homeowner’s. If the leak is inside, the next steps (dye test, fixture inspection) are usually DIY.
When you’ll encounter this term
- Water-bill spike — meter test is step one.
- Pre-purchase inspection — buyers often request a meter test demo.
- Vacation home — SPU AMI smart-meter alerts notify owners remotely of continuous flow.
- “Ghost flow” puzzles — the appliance auto-cycles you forgot to disable.
- Insurance claim — the meter timestamp helps document when you noticed.
Common variants
- Water meter leak test vs. toilet dye test. Meter test confirms a leak exists. Dye test localizes a flapper leak specifically.
- Manual meter reading vs. SPU AMI alert. Modern Seattle meters report continuous flow back to the utility and trigger an email alert. Many homeowners learn about a leak from SPU before the meter test happens.
Washington note
Most Washington homeowners own the service line from the meter to the building. That’s a regional wrinkle: in many other US cities, the utility owns the right-of-way segment. In WA, a leak between meter and house is your bill, and standard homeowners insurance generally doesn’t cover it. Locating that buried line on the meter test — by isolating with the building shutoff — is sometimes the most expensive 15 minutes you’ll ever spend.
SPU’s AMI (advanced metering infrastructure) program is now widely deployed in Seattle. AMI meters report continuous flow to a customer portal and trigger email alerts when low-volume flow runs uninterrupted. If you have an SPU account and an email address on file, you may be informed of a hidden leak before you suspect one.