1. Raise the stopper lever to the full upright (closed) position. Unscrew the retaining nut that holds the pivot rod to the sink drain. Pull the pivot rod out of the drain pipe to release the stopper.

2. Remove the stopper. Clean debris from the stopper, using a small wire brush. Inspect the gasket for wear or damage, and replace it, if necessary. Reinstall the stopper.

3. If the sink doesn't drain properly, adjust the clevis. Loosen the clevis screw, and slide the clevis up or down on the stopper rod to adjust the position of the stopper. Tighten the clevis screw.