Thanks guys. All parts of the siphon except for the top of the vent pipe are under a minimum 4" of water with no signs of whirlpools. I removed the intake pipe at the elbow that's held with screws (It's the elbow at water level, nearest the intake pipe.) There were no obstructions that I could see and the draw was pretty weak.
This system has (4) 90 degree elbows. Could that be the problem or is that standard?
Ryan, there is no vent hole.
At this point I'm going to have to try to work with the emergency spillway I guess.
