Should I shut off my water during a plumbing emergency?

When to shut off the main vs. just a fixture valve

• Leak at a single sink, toilet, or appliance with an accessible shutoff → close that fixture's valve only
• Leak location unknown, or it's behind a wall or under the slab → close the main
• Multiple fixtures or areas affected at once → close the main
• Any leak reaching electrical outlets or panels → close the main and cut power to that area

Where to find the main shutoff

• In the meter box near the street (may need a meter key, often sold at hardware stores)
• On the exterior wall where the supply line enters the house
• In a garage or utility room, or under a sink for fixture-level stops

How to close it

Turn a gate valve handle clockwise until it stops; turn a ball valve lever a quarter turn so it sits perpendicular to the pipe. If a valve is seized or won't budge, do not force it — forcing a corroded valve can snap the stem and turn a leak into a much bigger one. Call the utility or a plumber instead.

Does shutting off the water interfere with diagnosis?

No. A plumber can diagnose most leaks visually, by pressure-testing after arrival, or by briefly reopening the valve under supervision. Leaving water running to "show the plumber where it's coming from" only adds damage and rarely helps identify the source any faster.

Common mistakes

• Waiting to see if a small leak "gets better" before shutting off water
• Shutting off only the water heater instead of the main when the leak source isn't confirmed
• Not knowing where the shutoff is before an emergency happens — locate it now, not during a leak