I WISH I had a house already so I could go RO/DI with my water. What are you doing with the waste water?
My roommate and I were discussing how we would handle the waste when I get a place. Most likely I'll have a holding tank for the good stuff and the waste. The waste will be plumbed in on the line that feeds the hot water heater. When the tank has water in it, it will run through the heater. Then when it gets low enough, a float switch will activate a PLC controller that will flip the feed over to the main line from the water main.
Pretty cool idea. The water will be a little hard but for showers and such that's not a big deal. If I'm running a tank heater there's a softening effect with water being heated in the presence of copper anyways. I'm not sure how it will work in a tankless configuration though.