How to Replace a Bathroom Sink Drain Assembly

Step 1: Make sure the drain assembly is the problem

1. Look under the sink and around the drain opening after running a small amount of water.
2. Confirm the leak is coming from the drain body, the flange at the sink opening, or the drain tailpiece connection rather than from the faucet, supply lines, or the trap itself.
3. Check whether the stopper is worn out, the drain body is corroded, or the threaded parts are damaged enough that tightening will not hold.
4. Place a bucket under the trap and clear out stored items so you can work comfortably.

If it works: You have confirmed the bathroom sink drain assembly is the part that needs replacement and the work area is ready.

If it doesn’t: If the leak is coming from the P-trap, supply lines, or faucet connections, fix that part instead of replacing the drain assembly.

Step 2: Disconnect the trap and remove the old stopper linkage

1. Put the bucket directly under the trap.
2. Loosen the slip nuts on the trap and lower the trap section enough to drain out standing water.
3. Disconnect the horizontal pivot rod from the drain body and unclip it from the lift rod if your sink uses a pop-up stopper.
4. Pull the stopper out from above the sink and set the linkage parts aside in order so reassembly is easier.

Step 3: Remove the old drain assembly

1. From under the sink, loosen the large locknut that holds the drain body to the sink.
2. Push the drain body up while lifting the flange out from above the sink.
3. Peel away the old plumber's putty or sealant from the sink opening and from the old drain parts.
4. Clean the sink opening thoroughly so the new flange can seal against a smooth, dry surface.

Step 4: Install the new drain body and flange

1. Dry-fit the new drain assembly first to make sure the threads, tailpiece length, and stopper style match your sink.
2. Apply plumber's putty under the new flange unless the replacement drain uses a different sealing method provided with the part.
3. Set the flange into the sink opening from above and hold it centered.
4. From below, install the gasket and locknut in the order supplied with the new drain assembly.
5. Tighten the locknut until the drain is snug and stable, then wipe away excess putty squeezed out around the flange.
6. Keep the pivot opening aimed toward the back of the sink so the stopper linkage will line up correctly.

If it doesn’t: If the flange rocks or will not sit flat, remove it and reclean the sink opening before trying again.

Step 5: Reconnect the stopper and drain pipe

1. Insert the stopper from above the sink.
2. Reconnect the pivot rod and linkage under the sink, then adjust it so the stopper opens and closes smoothly.
3. Reconnect the trap and any slip-joint connections to the new drain tailpiece.
4. Hand-tighten slip nuts first, then snug them slightly with pliers without overtightening.
5. Wipe every joint dry so even a small leak will be easy to spot during testing.

Step 6: Test the repair under real use

1. Close the stopper, fill the sink partway with water, then release it and watch the drain body, tailpiece, and trap while the sink empties.
2. Run the faucet for several minutes and check again around the flange at the top of the sink and every joint below.
3. Touch each connection with a dry paper towel to catch slow drips that are hard to see.
4. If needed, snug a leaking slip nut slightly or reset a joint that is cross-threaded or out of alignment.
5. Check again after the sink has been used later the same day.

If it works: The sink drains normally, the stopper works, and no water appears around the flange or under-sink connections during repeated use.

If it doesn’t: If a leak continues at the flange, remove the drain and reseal it. If a leak continues at a pipe joint after careful realignment and tightening, replace the worn washer or affected drain piece.