I saw the pictures of the setup in the other post and it looks very good. I also want to use the 4in pvc pipe for a hydro system. Did you use the pipe with pre cut holes in it or did you cut them yourself? The baskets look to fit nice and snug.
When I first saw the pictures I was wondering which was the fill line and which was the overflow line. By your question I am assuming that the pvc (bottom) one is the drain and the red (top) flexible line is the fill line. I am no expert but I think you will find, if you reverse these and make the top the overflow and set it at the height that you want then make the lower one the fill line it will work just fine. When the
pump shuts off the
nutrient solution should siphon back through the pump into the holding tank draining the growing chamber (4in pvc pipe).