You Wildcats like to over think things! JUST KIDDING!

Just take two lengths of 4" sewer and drain PVC, use two elbows, two test plugs, turn it upside down in the water to fill it, put one side in the overflow, pull the test plugs (POND SIDE FIRST!!!!!)and watch 'er go.

Cut the length for the pond side about 3" longer than you want it drained and the part you put in the overflow about 2-3' longer. Essentially you'll be making an oversized U-Tube siphon.

Total cost should be under $25.