We installed two 4" PVC pipes in the dam, at water level. These pipes extend into the pond about 15 ft deep. Each PVC pipe has a 3' section on the deep end with dozens of 1" holes drilled, and the end of the pipes are capped. On the dry side, the pipes extend all the way to the bottom of the dam and discharge into the creek. These pipes easily handle the normal inflow into the 7-ac pond, and can be converted to siphon mode by closing off the "burp pipes" to pull the water level down when needed. Big rain events do exceed the capacity of the 4" PVC pipes, we have a concrete spillway for that. A series of rebar pieces at the spillway has been adequate to prevent grass carp from escaping. So far, we haven't had any trouble with the drilled PVC intakes plugging... although it seems inevitable eventually.
