The plunger piece provides the plug in the sink's drain assembly, keeping the water that runs into the sink from draining out. You must detach the plunger from the sink's drain assembly in order to clear out large clogs or to replace the rubber pad on the underside of the plunger. Reattaching the plunger in the sink requires almost no tools and only a few moments of your time to complete, making it a simple task for a homeowner.
Examine the plunger to determine how it attaches to the sink's plunger mechanism. You should see a small hole or loop at the bottom of the plunger piece.
Get underneath the sink itself with a flashlight. Find the pivot rod, or the rod that runs horizontally into the sink's drain.
Untwist the retaining nut on the pivot rod so you can slide the rod out of the drain assembly. If you cannot loosen the nut with your hands by turning it counterclockwise, use a pipe wrench to loosen it.
Insert the plunger into the sink's drain as far as it will go and pull up on the push rod on the sink. Insert the pivot rod into the drain assembly.
Keep one hand on the pivot rod and use the other to move the plunger up and down in the drain slightly until you feel the pivot rod slide into the hole or loop in the bottom of the plunger.
Tighten the retaining nut by hand while maintaining the plunger piece at the same height, preventing the pivot rod from slipping out of place. Test the connection by pushing up and down on the push rod and watching to see if the plunger moves up and down in the drain.