Never had one fail. Periodic maintnenance as with any PH
is to take it apart at the impeller housing and clean it. An overnight soak in white vinegar will help clean out any buildup that a rinse and scrub don't get in the first round.
From the Drss Foster and Smith web site:
Basic Cleaning Steps:
Remove the pump from the system.
Remove filter from the front of submerged pumps and remove debris. Rinse with plain fresh water (no soap).
Remove the impeller housing cover to expose the impeller.
Remove the impeller and the magnet. Inspect them for damage and wash with plain fresh water (no soap or abrasives).
Wash out the impeller housing with plain fresh water (no soap or abrasives).
Reassemble the pump and re-install it in your system