Jet,
I would worry about the screws. If they are on the "intake" (suction) side of the siphon, even a small air leak can stop the siphon, because air is many times easier to pull up hill than water. The "outlet" (pressure) side is not as critical, but a 100% seal is still desirable.
If your siphon gradually stops on you, check for small air leaks at the screws or joints on the suction side.
