Nice set-up.
Is the corrugated pipe hooked directly to the box?
Has the pond ever filled from heavy rains to use the maximum potential of the regular overflow pipe?
Any plans for a trash guard?
Yes, the inlet control box is collar tied to the existing pipe.
Yes, heavy rains have actually put my existing outflow pipe under water completely, but the emergency spillway has never run (in the past 3 years).
And yes, I'm planning to build a trash cage around the new inlet control this weekend (probably hog panels bent into rectangle, secured with steel posts. Might even cover the top of the cage too)
