OK, well Twilly's post got me thinking about how to run the pluming for a vertical flood and drain system. The problem is with a typical flood and drain system the water is siphoned back into the reservoir when the
pump shuts off, but that wont work in a multi-level setup using just one pump. The top level would siphon back but the lower levels wont. So I came up with a way to run it so all the levels will drain when the pump shuts off, and only one pump is needed to flood the very top tube, and it just overflows into the lower levels flooding them as well.
But the key is that it dosen't rely on the water siphoning back through the pump at all. Each tube has its own "small drain line" that goes directly back to the reservoir. But the key there is that the small drain line is small enough that when the pump floods the tube, the pump fills the tube faster than the small drain line can drain the water. Then when the pump shuts off the small drain line will continue to drain the tube until its empty.
In each tube at the opposite end of where the water fills it, is a much larger overflow tube. This large overflow tube determines the height of the water level in it, and should be large enough so that the water can drain much faster than the tube can fill up. That way it will never overfill, and spill out of the holes with your plants in it. Each of these large overflow tubes drains down into the tube below it, continuing to flood each lower tube until it reaches the bottom level, then from there the large overflow tube just drains back to your reservoir.
That's the simplest way I can think of for running a vertical flood and drain system using just one pump. But depending on the height of the top tube in your system (from the pump in the reservoir), you'll just want to make sure you have a pump that can pump enough water high enough to flood all the tubes adequately. You can use any materials to build the system, so you don't need to fallow the diagrams exactly. The basic principal is that each level drains back to the reservoir through it's own small drain line, that drains slower than the tube fills up. Then the larger overflow tube sets the water level and wont allow it to overfill, at the same time the overflow tube drains down into the level below it, flooding that level too.