There are three methods you can use to seal a ball bearing:

The top half of the shaft shows a conventional lip or grease seal that has very limited life and will cut the shaft directly under the lip. See “fretting”

The bottom half of the shaft shows a non-contacting labyrinth seal that will not destroy the shaft and works well as long as the shaft is turning. Most of these labyrinth designs are not effective when the shaft has stopped because you a trying to seal with a “hole”.

The face seal offers positive sealing of both the oil in the bearing case and the water or moisture that is trying to get in.

Some designs are adjustable so that you can make impeller adjustment in open or semi-open impeller configuration, and others use magnets instead of a wave spring to hold the lapped faces together.

A fourth option is a face seal design that uses magnets to hold two lapped faces together