2 things that I can add is that the inlet end at 3' below the pond surface only sees 1.299 psi.

The last item is you might want to put a large bell mouth fitting on the intake end to prevent a vortex from forming. If one does, it'll suck air and will break the siphon on ya.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).