How to fix a main shutoff leak

Steps

Goal: Confirm the leak is at the main shutoff, identify the source, and fix a packing nut leak or know when to call a plumber.

• Locate the main shutoff—usually near the meter or where the line enters the house.
• Dry the area and watch where water appears. Good: Water at the valve body or around the stem—proceed to Confirm leak location.
• Bad: Water from the meter, curb stop, or nearby pipe—different leak. See Fix a main water line that leaks or call the water utility.

Confirm leak location

Goal: Verify the leak is at the main shutoff and identify whether it is the packing nut, valve body, or connection.

• Check whether the drip is from the packing nut (around the stem), the valve body (crack or corrosion), or a pipe connection.
• A drip that increases when you turn the handle points to the packing nut.
• Good: Packing nut leak—proceed to Tighten packing nut.
• Bad: Valve body or connection—call a plumber. See When to get help.

Tighten packing nut

Goal: Stop a packing nut leak by tightening the nut slightly.

• Use a wrench to turn the packing nut clockwise a quarter turn. Do not over-tighten—the handle must still turn.
• For a slow drip, you can try this with water on. If the drip is heavy, shut off water at the curb stop or meter first.
• Good: Drip stops. Monitor for 24 hours. Proceed to Verification.
• Bad: Drip continues—proceed to Repack packing nut.

Shut off at curb stop

Goal: Turn off water before the main shutoff so you can repack safely.

• The curb stop is at the property line, often in a box near the street. You may need a curb key.
• If you do not have access, call your water utility to shut off the water.
• Open a faucet to confirm no flow. When water is off, you can repack the packing nut.
• Good: Water off. Proceed to Repack packing nut.
• Bad: No access—call the water utility or a plumber.

Repack packing nut

Goal: Add packing string to stop a packing nut leak when tightening failed.

• Remove the handle (usually one screw). Loosen the packing nut with a wrench and slide it up the stem.
• Wrap packing string around the stem above the threads—two or three turns. Slide the nut back down and tighten finger-tight, then snug a quarter turn with the wrench.
• The handle should still turn freely. Reinstall the handle. Turn the water back on at the curb stop.
• Good: No drip from around the stem. Proceed to Verification.
• Bad: Still drips—valve may be too worn. See When to get help.

Check valve shuts off

Goal: Confirm the main shutoff fully closes.

• With water on, turn the main shutoff off. Open a faucet and check that water stops.
• If water continues to flow when the valve is closed, the valve seat is worn—call a plumber. The valve must be replaced.
• Good: Water stops when the valve is closed.
• Bad: Valve will not shut off—call a plumber.

When to get help

Call a plumber if:

• The leak is from the valve body or pipe connections.
• The valve will not fully shut off.
• Repacking did not stop the leak.
• You cannot shut off water at the curb stop to work safely.

Call the water utility if you need the curb stop turned off and do not have access.

Replacing the main shutoff requires shutting off water at the street—a plumber can coordinate with the utility. For other plumbing leaks, see How to find a water leak or Fix a main water line that leaks.

Verification

• No water drips from the main shutoff valve when water is on.
• The valve fully shuts off—water stops at fixtures when the valve is closed.
• The handle turns freely after tightening or repacking.
• No leaks at the valve or connections after 24 hours.