You can use the waste water to water your grass or garden. I use the waste water for my FW fish.
Carey, with respect. Look at those diagrams again. There is a sediment filter, charcol filter, UV sterilizer, Reverse osmosis membrane, then another charcol filter (for taste, lol). No DI resin. Which is good, as drinking DI water has been mentioned to be bad. Before I hooked up my RO/DI at home, I would run my 5 gallon bottle through a zero water pitcher. I still purchase drinking water from the kiosks, and the TDS is usualy 12-25 except one, which I believe did not filter the water at all. I was given a tour of a stand alone kiosk. The filters are 3 feet tall. For maintaining, all tha really needs to be done is back flush the RO membrane. I worked at a dialysis clinic, their filters were 6' tall and cost $10K. It was only RO though, otherwise I would have started a business with the water they dumped out every morning.