When the lift rod is pulled upwards, it pulls the pivot rod up as well. This pivot rod is attached to the stopper, which is pulled down, effectively sealing the sink. ... The seal that you can see in the graphic makes it so the water running down the pipe does not leak out into your bathroom.

How does a push sink plug work?

An automatic sink plug works thanks to a steel spring located inside. To fill the sink or basin with water, one needs to push the sink stopper - it will plug the drain. Pushing the stopper again releases the water. ... There's no need to pull the whole sink stopper out and no additional mechanisms are necessary.

How does a stopper work?

The lever operates a lift linkage that pulls on a spring. The spring pulls a rocker arm that raises and lowers the stopper (see the illustration above). Pushing the knob and the lift rod down causes the pivot rod to push the stopper up. Pulling the knob causes the pivot rod to pull the stopper down.