Setting up the 'old' system

We dragged the old hydroponic system out a few days ago, and then put it together.

We think we have it set, now it is a matter of getting the elevations set up. We ran water though with a hose the other day and it all held and the water did water things.
We now have to figure out how it all sets up together, with the drains and the like.

We have a very large farm tank, and a smaller 50 gallon tank, I am hoping to use the 50 gallon. The piece of pipe sitting on top in the above photo is what I think was used to fill when it was first used. We need to figure out how to re-attach so we can control the flow. We also need a pump.

This is a less confusing picture of the pipe, the piece closest goes into the system, at the T is the input and then the right side is the overflow.

Me trying to figure it out- Thanks to S for the photo

Looks like a trip to Lowe's this weekend, and maybe Harbor Freight.