I think 1" drains should work. Im no expert as i only have my one setup with drains like this.i have one full siphon, the one with valve closed part way, then the one with the air hose takes up the little bit of residual and if the water gets up just below the emergency drain (all the way to left) the airline gets submerged and creates a full siphon. Not sure if this is correct way or not but it works for me and have started and stopped probably 100 times just to be sure i dont have a mess.