How to Replace a Sink Shutoff Valve

Step 1: Confirm the shutoff valve is the problem

1. Look under the sink and dry the valve, supply line connection, and nearby pipes with a rag.
2. Turn the valve handle off and on once to see whether it is stuck, dripping around the stem, or leaking from the valve body.
3. Check whether the leak starts at the valve itself rather than higher up at the faucet hose or lower down at the trap.
4. If the valve will not fully shut off the faucet water, or it leaks from the body or stem, replacement is usually the right fix.

If it works: You have confirmed the sink shutoff valve itself is leaking, seized, or failing to shut off water.

If it doesn’t: If the leak is coming from the faucet supply line nut, try tightening or replacing that line instead of replacing the valve.

Step 2: Shut off the home water and prep the area

1. Close the main water supply to the house or the nearest upstream branch shutoff that actually stops water to this sink.
2. Open the sink faucet to relieve pressure and let the line drain down.
3. Place a bucket or shallow pan under the valve and clear out stored items so you can work without twisting the pipe.
4. Take a close look at how the old valve connects to the pipe so you can match the replacement style before removal.

Step 3: Disconnect the supply line and remove the old valve

1. Use one wrench or pliers to hold the valve body steady and another to loosen the faucet supply line nut from the valve outlet.
2. Let any remaining water drain into the bucket.
3. Remove the old valve according to its connection style. For a compression valve, loosen the compression nut and slide the valve off the pipe. For a threaded connection, unthread the valve while backing up the pipe if possible.
4. Inspect the exposed pipe end and wipe it clean so you can see whether the old compression sleeve and nut are still on the pipe.

Step 4: Install the matching new shutoff valve

1. Compare the new sink shutoff valve to the old one and confirm the inlet connection, outlet size, and orientation match.
2. If you are installing a compression-style valve, slide the nut and sleeve onto the pipe in the correct order, then push the valve onto the pipe fully.
3. Thread the compression nut onto the valve and tighten it while holding the valve so it points in a usable direction for the supply line.
4. Reconnect the faucet supply line to the valve outlet and snug the connection without overtightening.
5. Leave the new valve in the off position for the first pressure test.

Step 5: Restore water slowly and check for leaks

1. Turn the main water supply back on slowly while watching the new valve and the pipe connection.
2. Keep the sink shutoff valve closed at first and check the inlet side for drips or seepage.
3. Dry the valve and fittings again, then open the shutoff valve slowly and let water flow to the faucet.
4. Run both hot and cold as needed for this sink, then inspect the valve body, stem, inlet connection, and supply line connection with a flashlight.

If it doesn’t: If you see a small drip at a compression connection, gently tighten that connection a little more, dry it again, and recheck.

Step 6: Make sure the repair holds in normal use

1. Open and close the new valve a few times to make sure it turns smoothly and actually stops water to the faucet.
2. Leave the cabinet dry and check again after 10 to 15 minutes, then again later the same day after normal sink use.
3. Put items back under the sink only after you are sure no slow seep is forming around the new valve.
4. Keep an eye on the area over the next day for any delayed drips.

If it works: The new sink shutoff valve works normally, shuts water off, and stays dry during real use.

If it doesn’t: If the valve works but develops a slow drip later, dry the area, pinpoint the exact connection, and retighten slightly or replace the mismatched part if needed.