How to shut off the water to your house

Where the main shutoff is

The main shutoff is always on the cold line between the water meter and the first branch to a fixture, and where the meter sits tells you where to look.

Basement, cold climates. The service line comes through the foundation wall below the frost line, on the side of the house that faces the street, usually within a few feet of a front corner. The meter is inside, a short way along the pipe, and the shutoff is on the house side of the meter; many homes have a second valve on the street side of the meter too. In older houses it is low on the wall at knee height. In newer ones it is often up near the joists, followed by a bell-shaped pressure reducing valve.

Crawl space. Same path. The line enters on the street side and the valve is usually within reach of the access hatch or where the pipe turns up into the floor. If not, check outside at the hose bib closest to the street; some builders put the main stop in the wall behind it or in a small access panel.

Slab foundation. The line comes up through the slab into the garage, a utility or water heater closet, or the laundry room, on the exterior wall nearest the street. A common Sunbelt pattern is a vertical pipe rising out of the ground outside, next to the hose bib nearest the meter, with a valve and sometimes a pressure regulator in the same stack.

Meter at the curb. In warm climates the meter sits in a box at the sidewalk under a lid that a flat screwdriver lifts. Inside: the meter, the utility's valve on the street side, and usually a customer valve on the house side with a lever or wheel handle. The customer valve is yours to operate; the utility's, in most jurisdictions, is not.

Private well. No meter. The shutoff is at the pressure tank, where the line from the well enters the house, usually with a valve on each side of the tank. Closing the house-side valve stops water to the house; to stop the well itself, switch off the pump's breaker.

Condos and townhouses. Each unit normally has its own shutoff: a utility closet, under the kitchen sink, behind an access panel in a bathroom wall, or beside the water heater. If there is none, the building has a riser valve that maintenance controls. Find out which, and who has the key, before you need it.

If none of that turns it up, follow the pipe. Start at the water heater, trace the cold line backward against the flow until it leaves the house. The last valve before the wall or the floor is the main.

When the valve is stuck, spins, or will not close

The failure happens in three ways and each has a different answer.

The handle will not move. Do not put a pipe wrench or a cheater bar on a wheel handle; the stem snaps and now the valve is open forever. Spray penetrating oil where the stem enters the packing nut, wait a few minutes, and work the wheel back and forth in small movements, open a hair then closed, gaining a little each time. A ball valve that is stiff responds to the same patience with an adjustable wrench on the flats of the stem if the handle is missing. Never heat a valve with a torch; the packing burns and the valve leaks.

The handle turns but the water does not stop. On a gate valve this means the gate has corroded off the stem or the seat is too fouled to seal. There is no fix from the handle. Go upstream: a second valve on the street side of the meter, the customer valve in the meter box, or the curb stop through the utility. Then have the valve replaced.

It closed, and now it drips from the stem. The packing around the stem has dried out. Snug the packing nut (the hex nut the stem passes through) a quarter turn clockwise with a wrench. If it still weeps, leave a bucket under it and add the valve to the plumber's list; it will seal again once it is reopened, usually.

A main valve that fails any of these tests gets replaced with a full-port ball valve, which is an hour's work for a plumber once the utility has closed the curb stop, or with a pipe-freeze kit if the utility is slow. It is the single best plumbing upgrade in an older house, because every other emergency in this guide depends on it.

Automating it: where a smart shutoff valve fits

A valve you have to be home to turn does nothing for the leak that starts on day two of a vacation. There are two ways to make the main close itself, and the choice depends on the valve you already have.

An inline smart valve (Moen Flo, Phyn Plus) is a motorized ball valve with flow and pressure sensors in one body, cut into the main line just after the existing shutoff and the pressure reducing valve, before the first branch. It watches flow around the clock, learns the household's pattern, runs a nightly pressure test for micro-leaks, and closes on anything abnormal. It needs a plumber, an outlet within cord reach and Wi-Fi at the main. Your manual valve stays where it is, upstream, so you can still shut the house off by hand.

A bolt-on actuator (the YoLink kit) clamps over the handle of the ball valve you already have and cranks it shut when a leak sensor touches water. It is a homeowner install, runs on batteries, and keeps working with the power out. The catch is in the name: it needs a quarter-turn ball valve with a free-swinging handle. If your main is a gate valve, replace it with a ball valve first, and then the actuator is an afternoon.

Label it and test it twice a year

• Tag the valve. A luggage tag or a label that says MAIN WATER SHUTOFF with an arrow for closed. Take a photo of it and its surroundings and keep it on your phone. Show every adult in the house, and the house sitter.
• Exercise it. When the clocks change, close the main fully, open a faucet to confirm the water stops, then reopen it. A valve that moves twice a year keeps moving. Do the same for the water heater inlet and the washer valves.
• Check the pressure. A hose-bib gauge, available at any hardware store, screwed onto an outside spigot or the washer valve should read between about 40 and 80 psi. Plumbing codes call for a pressure reducing valve when street pressure exceeds 80 psi, and a reading above that means the PRV has failed or was never installed; high pressure is what starts drips at the water heater relief valve and splits supply hoses.
• Walk the stops. Under every sink and behind every toilet, look for green crust or a wet spot at the stop, and replace plastic-nut supply lines with braided stainless ones with metal nuts.
• Before a long trip. Close the main, or at minimum the washer valves and the water heater inlet, and set the heater to vacation mode. A closed house cannot flood from a supply line. If the house has a fire sprinkler system or a boiler with an auto-fill, ask the installer what may be closed.

When to call a pro

Call a plumber if the main is a gate valve of any age that you have not successfully closed, if the valve spins or weeps after you operate it, if there is no shutoff at all between the meter and the house, if the pressure gauge reads over 80 psi, or if the service line is galvanized steel or lead, which a licensed plumber should be the one to touch. Call the water utility, not a plumber, to operate the curb stop; in most places that is free and usually quick for an active leak. If the water has already reached finished floors or walls, the first 24 to 48 hours decide whether it is a cleanup or a mold job; our 72-hour guide covers that part, and the form below reaches vetted local plumbers and restoration contractors through HelpMeNow.com.