Find your water main before the basement does

What the box says

Locate your main shutoff valve and turn it clockwise to stop the flow of water to your home. Allow two minutes.

What you will actually need

• A flashlight. Main valves live in the darkest corner of the house, behind the one box you promised to throw out in 2019.
• A second person. One at the valve, one at a faucet. It also gives you a witness.
• Towels and a bucket. The valve stem sometimes weeps a little.
• A paper tag and a marker, or a roll of painter's tape. You'll label the valve before you leave.
• A water meter key, only if your shutoff is in a ground-level meter box outside. It's a long T-shaped tool, and your utility or a hardware store can point you to the right one. This is the thing everybody forgets, and it's why you'll be driving back to the store with wet socks.
• A stick or a long screwdriver for lifting the meter box lid and poking around before your hand goes in. Spiders like those boxes.
• Penetrating oil, in case the valve hasn't moved since the Clinton administration.

The steps

1. Find it now, while nothing is wrong. In cold climates, the main line usually enters the house through a basement or crawlspace wall, on the side facing the street. Follow the pipe in from that wall. The shutoff is typically within a few feet of where the pipe comes in, often near the meter. In warm climates, where pipes don't have to dodge freezing, look outside near the foundation, in the garage, or in a meter box near the curb.

This is the step where you find out the valve is behind the water heater, under a pile of paint cans, and that your wife had put a tag on it three years ago. She'd also told you about it. Twice.

1. Know which kind of valve you have. A round wheel handle is a gate valve. You turn it clockwise, several full rotations, until it stops. A straight lever handle is a ball valve. It takes a quarter turn. The valve is open when the lever runs parallel to the pipe and closed when it sits crosswise.

1. Close it, firmly but without a fight. Turn the gate valve until it's snug and stop there. Don't crank it with all your weight. Move a ball valve the full quarter turn.

Righty-tighty, lefty-loosey. You know this. You'll still stand there and say it out loud, because that's what the valve wants to hear.

1. Open a faucet at the lowest point in the house and one at the highest. The water should run for a few seconds and then stop. If it keeps running at full pressure, you've shut the wrong valve or the valve has failed. Open the high faucet too, because it lets air in and the pipes drain faster.

1. If you're going to leave the water off for hours, deal with the water heater. Turn off an electric water heater at its breaker. Set a gas unit to pilot or its vacation setting. A tank that drains while the heating element is still powered can burn the element out. Do this before you drain the house, not after.

1. Tag the valve. Write "MAIN WATER" and an arrow showing the closed direction. Take a photo with your phone and keep it in a folder you'll remember. Tell everybody in the house, including the teenager who treats information like a rumor.

1. Turn it back on slowly. Open the valve a little, then walk to the highest faucet and let it sputter until the water runs clear. Then open the valve fully. Check for drips at the valve stem and at the fittings nearby. Run the hot taps for a minute to purge air.

The pipes will bang when you do it fast. They're not being dramatic. It's called water hammer, and it's the pipes telling you to slow down.

Once a year, close the valve and open it again. A valve that moves is a valve that works. A valve that's been frozen in place for fifteen years is a coin flip.

Where it goes wrong

The valve won't turn. Stop. Don't slide a pipe over the handle for leverage, because you can snap the stem and turn a leak into a flood. Put a little penetrating oil on the stem, wait, then try a gentle back-and-forth. If it won't move after that, it's a plumber's job. Better to learn that on a dry Saturday than during a burst pipe.

The valve turns but the water keeps running. An old gate valve can spin freely and shut nothing, because the internal wedge has corroded or broken. Your backup is the utility's shutoff at the street or meter box. In most places that valve belongs to the water utility, so call them. Many will tell you exactly where it is and how they handle emergencies.

It drips from the handle after you turn it back on. The packing nut behind the handle may have loosened. A quarter turn clockwise with a wrench usually stops it. If it keeps dripping, that's the plumber again.

When to call a pro

Call a licensed plumber if the valve is stuck, leaking, visibly corroded, or won't fully stop the flow. Call one if you can't find any shutoff inside the house at all, or if the only valve you have is an old gate valve and you'd like it replaced with a ball valve. Replacing a main shutoff often requires cutting into the line, and rules on who may do it and whether a permit is needed vary by city and state. Check locally.

One thing, stated plainly. If a pipe has burst and water is reaching outlets, appliances or the electrical panel, don't wade in. Shut off the main only if you can reach it while standing on dry ground. Cut power at the breaker only if you can reach the panel without stepping in water. If you can't, leave and call the utility and an electrician.

The shutoff is one piece of staying ready. Stored drinking water is another. The seventy-two hour kit covers how much to keep. A plumber on short notice costs money, so it helps to have cash you can actually reach. And if your parents live alone, walk through the house with them and show them the valve. That's a better gift than another set of towels.