Hogfan, an automatic start/stop siphon has a small pipe for a "siphon break'" and is set at a few inches above "full pool" water level.
Water will always raise or lower in the main pipe, because the atmosphere forces the water up the inlet (water always seeks it's own level and is the water level is the same inside the pipe as it is outside it)
When the vent pipe is under water in a rain event, AND the pool level reaches the bottom of the highest siphon pipe point, the siphon automatically starts.....when the pool lowers, and the vent sucks air, the siphon stops and becomes a "normal" drain again.
Edit:
A siphon inlet and vent pipe need good trash guards to eliminate the possibility of a clog...if an inlet plugs from a turtle or fish, the dam could get breached...if a vent gets plugged, the pond lowers to the inlet level of the siphon. A 45* angle pipe on the outlet that pools and "seals" to stop air entering from the outlet is a must also, or the siphon will hammer from stopping and starting over and over
Heppy, I don't understand why you have so much depth for your vent tube.....
Last edited by Rainman; 08/25/18 05:18 AM.
