A question for you, Reebok.

In that exploded view you linked, it appears that callouts #4 and #8 both would be contacting #5. Am I right? If that is true, then you probably need to look VERY closely at the area where they would be touching #5. If there is even the slightest deformation there, you would get a slow leak.

As I don't have experience with pool pumps, I am going by my experience with industrial and automotive equipment.