I am in your situation and I am going to install a pond dam piping system like the one displayed at ponddampiping.com. I was just wondering if anyone has first hand experience at this. I am going to make my own rather tahn order froum these folks. I believe I am going to use 8" PVC through the dam and a 10" riser and fit it with a 14" mouth and strainer. I can buy the sheet PVC and make my own anti seep collar. and so on