The 2am pipe burst is not the moment to learn where your shutoff is. Five minutes today saves five figures of damage some night you didn't plan for.
The three possible locations
| Location | Most common in | What to look for |
|---|---|---|
| Interior shutoff | Cold climates (basements, attached garages) | Brass or steel valve with wheel handle or ball-valve lever on the cold-water service line where it enters the house. Often near the water heater or the front basement wall. |
| Exterior shutoff | Warm climates (slab foundations, no basements) | Often outside near the water heater, under the kitchen sink, or in an outdoor access panel. Sometimes inside a small box mounted on the exterior wall. |
| Curb stop | Older homes, no interior shutoff installed | Buried valve at the property line. Small iron or plastic lid in the sidewalk or lawn marked "WATER." Requires a curb key (long T-handle wrench, $20 at any hardware store). |
Test the valve under non-emergency conditions
- Close the valve fully (clockwise). Ball valves: 1/4 turn. Gate valves: many turns.
- Try a faucet. Water should stop within 30 seconds (residual pressure drains).
- Re-open by turning counter-clockwise until firm, then back off 1/4 turn. Never leave a valve at full-open under pressure — the seat seizes long-term.
If water keeps running with the valve fully closed, the valve has failed. Common on gate valves over 10-15 years old. Replace before you need it ($200-$400 plumber). Modern ball valves don't fail this way — recommend upgrade if you have an old gate.
The curb key
If you can't find an interior shutoff or the interior one has seized, your only option is the curb stop. Hardware store, $20, long T-handle wrench with square socket. Buy one BEFORE you need it. If your main breaks at 2am and your only shutoff is the curb stop, you don't want to be driving to Home Depot in slippers.
Curb stop access: small iron or plastic lid in the sidewalk or lawn marked "WATER." Lift the lid (sometimes pry — use a screwdriver), insert the curb key, turn clockwise to close. Some utilities lock the curb stop — call the utility's emergency line and they'll send someone (free).
The vacation drill
For trips longer than 3 days, close the main. Eliminates the catastrophic-burst scenario while you're away. Drain the lines by opening the lowest faucet after closing the main. On return: close all faucets, open main slowly, run cold-side cleanup first to flush sediment.
Smart water shutoff systems (Flo by Moen, Phyn Plus) do this automatically — they close the main when they detect leak signatures or you flip a vacation mode. See Flo by Moen review for the auto-shutoff option.
FAQ
Where is my main water shutoff?
Three locations: interior shutoff (basement/garage), exterior shutoff (kitchen/water heater area), or curb stop (property line, requires curb key).
Should I close the main when on vacation?
Yes for trips >3 days. Eliminates catastrophic burst risk. Drain lines after closing.
What if my main valve won't fully close?
Old gate valves seize. Replace before emergency. $200-$400 plumber. Upgrade to ball valve.
How do I get a curb key?
Hardware store, $20. Buy BEFORE you need it.
Related guides
- Flo by Moen review — auto-shutoff systems
- Best water leak sensors 2026 — detection layer
- Water heater leaking — diagnostic for the most common emergency shutoff scenario
Editorial standards: Reviewed by Al, Building Doctor — IUOE Local 39 Stationary Engineer.