My "improved" drawing may not be to scale either. I need to re-look at the length of the 4" pipe to see how tall it is. I recall that the top of the 4" pipe is significantly below my overall dam height + I think it is well below my emergency spillway too. Needs a look see and test when lake is full.

My Emergency Spillway is approximately 10' wide by 5' deep

Looking back, I think my first inclination was right - I dont get this siphon stuff.

But I think I now understand much better, thanks guys.

- Smoke 'em if you got 'em

[Linked Image from i4.photobucket.com]