This is all very good info. We had a frog-floater of a rain last week, so I went down to see my 12" siphons working. The air vents were 5-6 inches under water. I was disappointed at the flow. It looked like the 1st video GW posted. I believe I have the same problem he did because I only have a 22 1/2 degree elbow at the discharge end and air is running back up the pipe. I have the same gurgling sound too. Fortunately, I have a couple of 45 degree elbows left over. I will put them on and report back.
