When pipes burst, fixtures leak, or appliances cause a flood, stop the deluge by cutting off the water at its source. Take a moment to locate all of the shutoff valves in your home so you'll be prepared for an emergency.
Whole-house shutoff. For a home served by a well, the shutoff will be on the house side of the pressure tank. You should also cut power to the tank so it doesn't detect a phantom pressure loss and burn out trying to compensate. In a home with metered water, look for the shutoff on either side of the water meter.
Remember, your meter could be located in the basement, mounted on an exterior wall, or even out near the street in a concrete "meter pit" where the household feed line meets the utility main.
Whole-house hot-water shutoff. On your water heater there should be a valve on the hot-water outlet, which controls all of the hot water to the house. If there isn't one on yours, you or your plumber should install one.
Toilet shutoff. Look for this inline shutoff — typically a ribbed oval handle — under the toilet tank.
Sink shutoffs. These inline shutoffs usually sit just beneath the sink or within the cabinet or vanity. The one on the left is usually for the hot water, the one on the right for cold water.
Dishwasher shutoff. Look first under the kitchen sink. Often there's a reducer coupling and shutoff valve leading to the dishwasher on the 1/2-inch hot-water sink-supply line. Not there? If you have a basement, look between the ceiling joists just below the appliance.
Clothes washer. There should be valves where the house-supply lines meet the washer hoses. Washer hoses are notoriously weak, so always close the valves when leaving home for an extended period.