Just stumbled on this thread, great idea. I'll have to run the wires from the AC float switch and the R.O. output under the house between the bathroom and living room for my set-up. It's probably a 10 ft run at the most. Regarding the brass parts, this is easily addressed by putting the solenoid on the input side of the R.O. unit. That way, you're subjecting municipal water to the brass, not R.O. water. It does mean a length of wiring between the float switch and the solenoid, but that's okay, don't you think?
THANKS for such a great idea. Oh yeah, for those who want to install this thing leak free in a sump wall, I'd definitely avoid tapping the acrylic. This stresses acrylic, and eventually it'll fail. If you don't want to use a bulkhead, just get a PVC 3/4" or 1" slip X 1/2" thread adapter. Drill your sump for that, and install it with weldon # 40. Just put a bead of #40 around the "flange" part of the adapter, like where the gasket on a bulkhead goes, set it in place, and give it a gentle twist to spread the cement. It'll last forever. In fact, in acrylic sumps, you could do away with bulkheads altogether and just use these PVC bushings and weldon #40. If one were to break, oh well, but that's unlikely.
Matt