regardless of what happens inside the S-curve, the opening ends up getting a slight vacuum from suction, but there is no such suction on the opposite side. Ima

regardless of what happens inside the S-curve, the opening ends up getting a slight vacuum from suction, but there is no such suction on the opposite side. Imagine the S is straight, but a vane attached to the side of the pipe blocks suction from one side. I tried to illustrate this in ascii art, but it appears HN has an algorithm to destroy ascii art. That vane will now have a slight vacuum on the side of the pipe, and it seems logical that it should want to move in that direction. Now imagine that vane curved around the pipe so it forms the end of the S-bend. Same thing.