My Skuma RO water certainly retains something. The TDS of my tap water, measured daily over the last two weeks, has ranged from 186 to 258, while the RO has ranged from 65 to 72. I make that a filter efficiency of no better than 75%. In the same period, the TDS of the coffee-minerals water has ranged from 94 to 107 (usually in the 90s).
Of course, what matters most is what’s in that TDS (whether from plain RO or coffee-minerals RO). I’ll have to measure that sometime or send it out to be professionally analysed.
