The main water shutoff is usually near the point where the supply line enters the home, but its location varies with climate, construction type, and meter placement. It may be in a basement, garage, utility room, protected exterior wall, or meter box. Finding it before a leak is far easier than during an emergency.
Trace the supply line from the meter or entry point
If the meter is indoors, look for a valve immediately before or after it depending on the installation. If the meter is outside, identify where the service line enters the building and check the matching interior area.
In cold climates it is usually inside conditioned or protected space
An exterior valve exposed to freezing would be vulnerable, so many cold-climate homes place the shutoff in a basement, garage, or utility area. In mild climates it may be in an exterior box or beside a wall.
Distinguish the house main from appliance shutoffs
Valves under sinks, behind toilets, or near the water heater isolate only a branch. The main should stop flow throughout the home, which can be confirmed by opening a faucet after closing it.
Label the valve once you find it
A visible label and a photo help anyone in the household act quickly. If the valve is corroded, will not turn, or does not seal, have it repaired before a leak turns that problem into an emergency.
Sources
- U.S. Environmental Protection Agency WaterSense — Home Maintenance — Household maintenance related to water, leaks, toilets, pressure, and efficient use.