I have seen this same set up done on other forums with what looked to be 4" PVC and he did great with it. Unfortunately I did not see anymore about his "system" as after the initial grow post he started to show more of the plant when all I wanted was more info on the system lol.
Problems I see with this is the roots clogging everything up (good picture to see is that Bubble Bucket tut as the whole 5 gallon bucket is filled). I have done hours of research. 4" PVC is as big as it gets I think the larger ones are ABS I think and dam they get expensive. I thought about doing it in those storage bins but I heard the sprinklers do not penetrate enough to get to the center of the root mass, and with this it kind of soaks the roots when it runs off to the drain. But I hope you keep us updated because I would liek to learn from your mistakes
Or Pm with any updates thanks in advance mate.