I installed a 2” PVC drain under my pond dam while it was under construction. The intake is a vertical pipe with ¼” holes drilled into it standing up about 4’ off the bottom at the deepest point. It is surrounded by a 24” diameter plastic pipe that is filled with 1.5” rock to “filter” the water going into the drain. The outlet is a 2” PVC ball valve ending with 2” pipe thread which I can attach a flexible hose (I have two of Harbor Freight’s 2” suction hoses). The outlet is set behind the base of the dam about 3’ down in the ground inside 24 inch diameter pipe with a lid on it. I have an attached “T” handle to open/close the valve.

It worked well to keep water from building up in pond before the dam was done, and I occasionally use it to lower the pond water for projects. Initially I thought I would use it to fill water tanks but have a better source now.

The water coming out from the bottom of the pond does have that somewhat rotten egg smell. I'll open it up and let it run sometimes in the summer if there is water to spare.