I got a clear check-valve for my return from the sump back to the tank....... ($30 at aquarium store and I see white PVC ones at hardware store for $7 but I digress)
they normally get clogged up and fail, don’t count on them, they let you down when you need them! If I read correctly this will only save the water in your return line anyways
With a bean-animal style should I have any of these on the overflow return lines? I bought it one gate valve already for the return line from overflow per a video I saw.
No, you shouldn’t need them
Also, it said to put those threaded screw-off connectors on each return line, so I got 3, but are these necessary? What scenario wiuld I need to completely remove my plumbing to my sump? Just to clean out etc?
yes in case you need to disassemble for some reason