I really hate to sound stupid here but what is a loop siphon???

I am trying to figure out the need for the pvc to go all the way thru the growbed... Does it go through to both sides or only one?? sorry just trying to visualize something I have never seen before...

I am a great one for looking at something and then going home and doing it myself, but I am totally lost here.

It took me a while but I finally understand how the auto-siphon works and can get them to work now no matter how tall my stand pipe is but I just cant picture a loop siphon.

Would have killed me to cut up those totes, but if what you are doing looks great I will copy your design and give it a try.

Thanks
Sheryl