To repair a bathroom sink stopper, begin by dissembling and cleaning the stopper assembly, before reassembling and adjusting it. Tools needed include a screwdriver, slip joint pliers, a brush, a permanent marker, a sealant, a cleaning solution and the replacement stopper.
Shut off the water supply to the sink, and loosen the top retainer nut on the P-trap. Remove the horizontal pivot rod from the drainpipe, and mark the point where the clevis connects with the stopper rod, using a permanent marker. Loosen the clevis screw to remove the clevis. Soak the horizontal pivot rod and the clevis in the cleaning solution.
Lift the stopper out of the drain, and inspect the rubber seal on the stopper head. If the seal is cracked or brittle, replace the stopper; otherwise, reuse it after cleaning it, using a mild cleaner and a brush. Then clean the clevis and horizontal pivot rod.
Remove all of the old sealant, and discard the old finished flange. Replace the flange with a new one.
Insert the old or replacement stopper into the drain, and slide the clevis over the stopper rod. Insert the horizontal pivot rod in place, and tighten the clevis screw at the spot marked with the marker. Ensure that all moving parts have been reattached.
Tighten the retaining nut enough to prevent the stopper rod from sliding down. Loosen the clevis screw, and pull the stopper rod up, before sliding the clevis up the stopper rod and tightening the clevis screw. Adjust the retaining nut and the clevis to get a good seal.