Some water pumps use ceramic impeller shafts, while others use stainless steel. Both serve the same purpose and both have their advantages, but it’s their disadvantages that really separate the two. Ceramic shafts, for example, can easily break. This sort of thing happens quite a bit when removing the impeller for cleaning, or times when the impeller gets hung up. Stainless steel impeller shafts, while far more durable than their ceramic counterparts, are subject to bending and rusting. The rust is not quite as common a problem, but like the ceramic shafts, when performing maintenance on the skimmer, the stainless steel shaft is subjected to stresses that can cause issues. In either situation, be careful when taking skimmer pumps apart for maintenance, and always keep a spare around in the event something does go wrong.