Gator,

I understand your description and drawing but I think you will find a problem with the way it is setup. I may be wrong, but any hole allowing water to enter the 4" pipe will not be enough to completely seal off the 4" pipe starting the siphon. The 4" pipe would have to be completely covered or underwater for the siphon to start.

The slightest amount of air entering the 4" pipe will break the siphon or prevent it from starting.
Was there a reason you went to 4" pipe? A 1/2" "U" will do the necessary job of starting the siphon once the water level rises to block off any air entering it.

I hope your pond fills up soon and please let us know how the 4" works.

Dan

Mistakes are proof that you are trying.


Dan