OK Dan and Jersey,

Unfortunatly my second drawing is fairly accurate. I think the 4" siphon pipe is too tall and will cause a big whirlpool as mentioned above which will take the lake level around the same height as the spillway. Additionally the 4" pipe dosnt have nearly enough holes in it.

I have Vaccum Breaker and doubtful I will ever draw a siphon in current design. The 4" pipe is way too tall. Hello spillway. I'm thinking that I'm going to pull out the 4" and either cut it down or replace with "upside Down U" to make sure I pushing as much water as possible thru the pipe.

Can anyone tell me a way to calculate the difference in thru-put for a drain vs. siphon? Is is 1x, 2x...?

- Smoke 'em if you got 'em

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