Well folks, i have an answer and schematic for everyone. Well I think i do. I applied my Nuclear Power/Engineering Background to the problem and came up with a way for everyone to do this, and make water changes/automatic level simple. Here is the schematic:
First thing is to get the water to the basement, thats simple, just run the PVC through the wall. Use one long piece in the wall, to make sure there arent any joints to leak, etc. Then connect the drain to the PVC using flexi tubing, etc. I would use no less than 1" PVC for the drain. In my example i used a tank that had 2 drains that i would T together to one and then split again at the bottom where the fuge/sump is. Gravity does all the work here folks. At the fuge i split it again, one drain going to the skimmer area, and the other to the fuge area. I install ball valves at the drains to control flow to each, i.e. a little to the fuge and a lot to the skimmer area. At this point its your typical sump/fuge.. water flows from the sump to the return area in the middle and from the fuge area to the return area. Simple.
The return is challenging because you will need no less than 2 good pumps. One near the ceiling of the basement and one in the sump. The one in the sump needs to put at least 10X your tank size in flow at the height of the ceiling in the basement. I.E. if you have a 125GAL tank, it needs 1250 gallons at say 8 ft. This pumps sole purpose is to provide Net Positive Suction Head to the second pump at the ceiling of the basement. Net Positive Suction Head is the water required to make the pump work, thats as technical as ill get here. The second pump should be mounted very high in the basment, on a strong shelf or something. This pump will actually push the water into the tank. This pump needs to be like 12X the flow rate at a height from the pump to the tank, i say 6ft to be safe. As explained above to account for head loss in the SCWD (explained later) and for headloss in the return nozzles. After the second pump there should be a ball valve inline to help control water flow back into the tank, in case the pump puts out a little more than the tank drains. After the valve close to the returns at the display tank, i recommend a Switching Current Water Director, or SCWD. This will at random intervals switch returns back and forth creating a good strong current and eliminating the needs for power heads in the tank. I love these things, and they work really great too. Thats it for the returns.
But now you ask, whats the WASTE WATER LINE coming after the first pump. Great question, that is a line to make water changes SIMPLE. Basically there are two valves, the fist one you fully open and the other you throttle open. The pressure at the outlet of the first pump will push water out of this line and drain water from the whole system to a sink drain or bucket etc. No more need for siphons, and the system can stay on the whole time! You will probably want to shut the second pump off when water quits draining from the display tank so you dont cavitate or damage the pump. When you drain enough water out, you shut the valves. Then add saltwater as appropriate, and start the pumps again.
Now look at the RO/DI resevior thats connected. Thats a source of make up water for evaporation. It uses a kent marine mechanical float valve and the weight of water to refill the sump. As level lowers due to evaporation the valve floats down, opening the valve allowing RO/DI water to flow in from the resevoir to the sump keeping level constant and therfore salinity constant. The RO/DI unit also uses the kent mechanical valve to keep level in the resevoir constant too... works on the sampe principle. Now you have to pin the valve in the sump in shut when doing a water change, but it will be right there next to the other valves you operate to do it, so no big deal.
This is just one way to do this, i think you can come up with a thousand ways to do it, but this is my way.
