These are just the very basic principles of a siphon. You will also want to make some sort of "trash rack" on the inlet of the main pipe and vent opening to ensure they never plug up.
If the main inlet plugs, or worse, a stick or turtle gets trapped in a curve, then water will not flow properly and could lead to a dam breach and difficult repairs. If the vent plugs, the siphon will not stop till the pond drains completely, or the lift is too high to overcome and water either vaporizes or the tubing itself collapses from the vacuum pressure.
Rainman,
I don't know what your occupation is so forgive me with this question; have you installed bottom withdrawal systems? The reason I ask is because you live in the area and I could use a "consultant" on my pond build since my pond builder doesn't have experience installing a BWS.
