Morning, first let me start by saying I am only regurgitating info I've learned off the forum. You can of course get by with just RO water, unless of course your source water is that bad, which it isnt cause your in Calgary. But a RO/DI system will ensure that you start off with 0ppm or pure water. From what I have read though you would not want this to be your only source of drinking water, some of the minerals in the water are good for you. RO water I would think would be fine to drink as you can buy RO drinking water
As for the waste water I agree, it seems like such a waste. 5G pure water to 10G waste
. All I do to make myself feel better about it is use the waste water for other things in my house such as plants. My plan for the next house is to run the waste water to a rain barrel which I will use for outdoor gardening and the lawn. Im not sure if the number of stages or GPD rating effects the ratio of good/waste water, im sure someone on here will know.