no much simpler and WAY cheaper. I remembered how to make it. Now I need to figure out if I can run a 50' hose from my ro/di to my tank, or if that's too long of a run. Then I'll be looking for a float switch...
here's a diagram. it's not my design, I just couldn't find the thread I found it, can't even remember which site:
you need something to construct it out of (acrylic or glass), a means to drill whatever material you choose, a float switch, and an air valve.
When it's filling, air can escape through the air valve. when it's full, the float switch will turn the RO unit off.
when it starts to drain, the large chamber is emptied only, because the air valve keeps the small chamber full, UNTIL the bottom is reached, where it fills it back up again.
you just do the math, and make it whichever size you want to hold.
still sourcing cheap float switches that are meant to be installed THROUGH aquarium glass (usually drilled with a 5/8" bit).