RAH,

It does have a notch at the top, not a large cut, but air can get in. Until I saw that notch I didn't understand how it could work. I thought it wouldn't allow anything in. With it notched I can see how the water level is forced into the open end and then pours over the exit pipe...but it's not as fast as an open ended pipe.

My day to day flow is fairly low because it's only a small stream. I measured the pond today and its just at one acre (~100 yards x 50 yards). Now that I have the overflow unstuck I can see what this design can handle and see how often it gets over the top of the overflow and if I ever get close to needing the spillway. Good question, this group is getting me just what I need, helping me think through this.


Tom Coleman
704-756-5659