Find a Hidden Water Leak With the Meter Test

Any movement with no water in use is a leak by definition.

Turn off every fixture and appliance that uses water, including ice makers and irrigation controllers. Read the meter, note the low-flow indicator if the meter has one, wait one to two hours without using water, and read it again. Movement in that window means water is leaving the system somewhere.

One valve halves the search area.

Close the main shutoff where it enters the house and repeat the reading. If the meter keeps moving with the house isolated, the leak is on the service line or an outdoor branch, which is usually a utility or licensed-plumber matter. If it stops, the leak is inside the house and the search continues fixture by fixture.

Most indoor leaks are visible if you look in the right five places.

Toilets first, then water heater and its relief discharge pipe, then supply lines behind the washing machine and under sinks, then any humidifier or filtration equipment, then irrigation valves and outdoor hose bibs. EPA WaterSense guidance points at the same short list because that is where the volume is.

Structure records a leak before a bill does.

Look for warm spots on a slab floor, unexplained damp or musty smells, staining on ceilings below bathrooms, a section of lawn greener than the rest, and a water heater that runs more than the household changed. Persistent damp is also a mould concern; EPA mould guidance covers drying and cleanup limits.

Two meter readings and a location beat a description.

Give the plumber or utility the two meter readings, the times, and whether the house-isolated test kept moving. Hidden slab leaks, service-line leaks, and anything requiring opening walls or excavating belong with a licensed trade; so does any leak near electrical equipment, which should be de-energized at the panel before anyone investigates.