For the most part yeah....I've heard some have a little more or a little less but you;ll still get more waste water than useable water for your tank. I'm just guessing at the 3g to 1g ratio on mine, but it seems about right.
Another $15 you want to spend is for a TDS
(total dissolved solids) meter. You can check your tap water against the ro
water and really see the difference. It's also needed to tell when the unit needs new filters. Mine puts out 0 ppm
and my tap water is at 243! So defintiely worth the money.