Whether you do a lot of repairs around your house or rely on reputable contractors to make them for you, you—and everyone in your family—should know how to turn off the water supply, gas and electricity to your house.

So before you have an emergency at your house that involves water, electricity or gas, take a few minutes to locate the shut-off valves for those utilities. Test them to make sure they’re in good working condition. Older valves that haven’t been touched in years can break, and it’s better for that to happen during a test run than during an emergency. Once you find and learn how to use your shut-off valves, share that information with everyone in the house, and place a colorful tag on each one so it’s easy to find when there’s no time to waste looking for it.

Here’s how to make sure you know how to stop the water, gas or electricity during an emergency while you wait for the plumber or electrician to arrive:

Water. Most water shut-off valves are located outdoors near the front door of the house. Look for a hose bib—it’s an outdoor water spigot where you could attach a garden hose. It might come up from the ground close to a wall of your house. Older models have a round on/off handle (valve), while newer ones have straight handles.

Turn it to the “off” position, and then go inside and turn on a water faucet. If water comes out, try turning the outdoor valve in the opposite direction. If that doesn’t shut the water off—or if the valve breaks when you turn it or if you can’t find it—call a plumber right away to resolve the problem now rather than waiting until you have an emergency at home.

That outdoor valve will shut the water off to your entire home, and you only need to do that during an emergency. If you’re repairing a faucet, a toilet or the washing machine, you’ll find shut-off valves under the sink or on the wall nearby that will kill the water supply just for that area. Usually, you don’t need to turn off all of the water in the house to make simple repairs.

Gas. The only reason you would ever shut off your home’s gas supply is if you smell or hear leaking gas. Once you turn off the gas, get everyone out of the house, and then call a qualified plumber or the gas company to resolve the problem. Do not re-enter your house until the gas company tells you it’s safe, and do not turn the gas back on or re-light your pilot lights yourself. Leave that to the professionals.

Your home has a gas supply only if you have gas appliances—like a gas stove, furnace or fireplace. If your home is all-electric, you won’t need to worry about gas leaks.

The service shut-off valve usually is located next to your gas meter, which is outside of your home on the side or back. Go outside and look for it now so you’ll know where it is in case of an emergency. Sometimes, it’s inside of a cabinet. If you can’t find it, call the gas company and ask.

The valve most likely will look like a lever. Use a 12- to 15-inch crescent wrench to turn the lever one-quarter turn in either direction so it’s perpendicular to the pipe.

Like water valves, you’ll also find gas shut off valves located near most gas appliances. Walk around your house and look for them now so you’ll know where they are when you need to. Sometimes, you can shut the gas off to a single appliance rather than to the whole house if you know which one is causing the problem. Rotate the valve one-quarter turn to close it.

Best bet: Get out of the house and call a plumber or the gas company if you suspect a problem. The professional will tell you if you should touch the valves or wait for help to arrive.

Electricity. If you do have a gas leak, it’s a good idea to shut off your home’s electricity as well as the gas. Likewise, if a plumbing leak floods your house, you’ll want the power off.

You can turn the electricity off inside your circuit breaker panel or fuse box. You would usually do this only in an extreme emergency.

Before you face that emergency, locate your box. It might be in a utility closet or the basement, if you have one. It’s a metal box full of switches or fuses.

If your box is full of switches, they control your home’s electrical circuits. Turn all of them to the “off” position, and then switch off the main switch at the top. In a fuse box, you’ll probably see only one lever among the fuses. Pull it down (off).

Two cautions:

• If your floor is flooded or if the electrical panel is wet, do not touch the panel.
• If you see exposed wires inside the box, do not touch them.

In both cases, call the electric company or an electrician to handle this dangerous task.

Don’t flip the main switch except for during an emergency. If you’re having a problem with electricity in a particular room or with one appliance, you can flip the switch that powers just that area. Often, you’ll find that the individual switch is “off,” and you can solve the problem by flipping it back on.

Don’t get caught during an emergency having to search for basic information like the location of your water, gas or electric shut-off valves. Often, switching the utilities off will save your home from damage while you wait for the professionals to arrive to repair the problem.