Pond Boss Forums POND CONSTRUCTION Renovating a Pond or Lake? Siphon How-To?

You don't really need any kind of valve with the P trap.

The issue is finding any of that 4 inch donkey dong that has absolutely no pin holes in it. One pin hole and it sucks air then fails eventually.

Then your math doesn't add up. Really you would need two 100 foot sections and some way to join them with absolutely no leaks. You are using a big chunk of 100 feet just getting over the damn.

Then there is building a simple eductor in the siphon line which enhances the flow. An eductor would fill the line and increase the flow.