You may have never even considered that your house has a central point to shut off the water, but it’s something you should locate long before you need it.
Whether or not you’ve ever used it, somewhere in the bowels of your home—be it in a utility closet, basement, crawlspace, or even in a service box outside—there is a valve that shuts off the flow of water from the street (or well) to the rest of the interior plumbing.
While you can stop a leak closer to the source (turning off the valves under the sink, for example), the surest way to stop any leak is to close the valve where it enters your home.
Although the valve can look different depending on the age of your home (it might have a wheel-style handle like those commonly found on outdoor spigots), the bar-style valve seen above is the most common modern design. You simply turn the valve so that the handle is perpendicular to the pipe to stop the flow of water.
Whatever design your shut-off valve has, locate the valve and test it out (to ensure it works correctly) before you’re frantically trying to stop the dishwasher from flooding the kitchen.