What does your air lock look like on the outlet end? Is it keeping air from entering from the outlet?
When it's flowing, but not siphoning, take a small 6' garden hose (or similar), cover one end with your thumb and put the other end up the outlet just far enough to get past the water level standing in the outlet. Once the hose is in there, release your thumb and see if the air pressure releases and starts the siphon.
I had to do this with mine recently. I'm considering a separate one way valve (check valve) at my cleanout (highest point) to let positive air pressure escape easily, but seal once the siphon starts.
Last edited by KY_pond; 03/04/21 02:43 PM. Reason: typo
