My whole system is raised up so I don't have any sumps for any of my beds. Currently everything dumps into a 4" drain pipe and goes back to the tank.

I want to add Bato Buckets to the system. They will be at ground level. I'm sure the piping will need to be at ground level and go to a sump somewhere. How do you decide on the size of the sump? How do you get the water back to the tank. I know pump it but how do you hook up the pump, with a float valve so it only drains it when it fills or keep it constantly going? Any other pointers to adding this to the system?

Just as a side though. How far away can these be placed away from the system?