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Where is my home's main water shutoff valve?

Updated August 2026

15 minutes · Easy DIY

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Trace the cold water line backward from your water heater to the wall where it enters the house, and the main shutoff sits within a few feet of that entry point. Fifteen minutes with a flashlight settles it permanently. In a basement home it is low on the street-facing wall; in a slab home, check the garage, a utility closet, or an exterior wall box; in warm climates there is also a curb valve in a lidded box near the street. Find it now, because a burst 1/2 inch supply line puts 5 to 8 gallons a minute into your floor.

What you need

Before you start: Old gate valves are the hazard here, not the water. A wheel that has not moved in fifteen years can snap its stem or weep at the packing nut the first time you force it. Turn slowly, stop if it binds, and if it drips afterward, snug the packing nut an eighth of a turn instead of cranking harder. Replacing a main shutoff runs $200 to $500. If the main stays off more than a day, switch the water heater off too, since an electric element that fires in a drained tank burns out in seconds.

Steps

  1. Start at the water heater and follow the cold inlet pipe backward. Every drop of water in the house passes through the main, so the pipe leads you to it.
  2. Check the street-facing wall of the basement or crawlspace, usually within 3 feet of the floor and near the outdoor hose bib. That is where the service line comes through the foundation.
  3. On a slab foundation, look in the garage, a laundry or utility closet, or behind an access panel on an exterior wall. A bell-shaped brass pressure reducing valve is a good landmark; the shutoff usually sits right beside it.
  4. Identify the type. A ball valve has a lever and closes with a quarter turn. A gate valve has a round wheel and takes 6 to 8 full turns, and it is the type that seizes.
  5. Test it. Close the valve, then open a bathtub faucet on the top floor. Flow should die within 10 to 20 seconds, and a steady dribble after a full minute means the valve no longer seats.
  6. Reopen it all the way, then back a gate valve off a quarter turn from wide open. That keeps the stem from binding in place over the next year.
  7. Tag the valve with bright tape, label it, photograph it with something recognizable in the frame, and text that photo to everyone in the house. At 2 a.m. nobody can follow a verbal description.
  8. Locate the backup while you are at it: the curb stop in the lidded box near the street, which needs a meter key and a quarter turn. Many utilities forbid customers from operating it, so treat it as an emergency-only option.

Or hire it out

A plumber charges $100 to $175 for a service call to locate and exercise the valve, and $200 to $500 to swap a seized gate valve for a quarter-turn ball valve. The locate itself is a 15-minute job you can do tonight.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for shutoff valve checks sets itself.

Log this task, get the next reminder

Frequently asked questions

The valve will not turn, or it leaks after I close it. Now what?

Do not force a bound gate valve; a snapped stem leaves you with no shutoff at all and an emergency call at premium rates. Get a plumber to replace it with a ball valve, which closes in a quarter turn and stays operable for decades. A weep at the packing nut after you move an old valve is common and often stops with an eighth-turn snug. Age matters: see how long a main water shutoff valve lasts.

Should I shut the water off when we travel?

For any trip longer than about 3 days, yes. Close the main, then open a low faucet to drop the pressure in the lines. In winter leave the heat no lower than 55°F, and put the water heater in vacation mode rather than fully off. A supply hose that lets go on day two of a ten-day trip is the most expensive plumbing failure a house can have: the cost of leaving town without shutting off the water.

How often does the valve need to be exercised?

Once a year, closed and reopened fully, which is enough to keep mineral deposits from cementing the stem. Add a test any time you have work done on the plumbing, since a valve you discover is dead during a repair is far cheaper than one you discover during a burst. Put it on the annual list with the water heater and the supply lines: how often to test a main water shutoff valve and the main water shutoff maintenance checklist.

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