I used PondDamPiping for my two 12" siphons. They were very helpful in sizing the system and with advice along the way. They even offered to buy back any pipe I didn't use, but I did use it all. Looking back, because of the huge, gentle slope of the land all around my pond, I could have gotten by with one 12" siphon, but we haven't had a hurricane go by here since the pond was built. And it would be a bit of a problem to get up one day and find water over the emergency spillway, which happens to be my neighbors driveway.

Hey Moe, I'm trying to think but nuthin's happening!