I've just purchased a 6 stage 100 GPD (nowhere near that) RO unit and have
ran it for a full day now most of that time was flushing the membranes and
the TDS readings were thus.
tap water = 210ppm
during flush = 10ppm.
after flush and tap switched to produce RO water = 11ppm.
now I have disguarded the first 40 litres of water and am now collecting the
RO in a water butt. the reading is still 11ppm but now I keep getting
static shocks when I get near the water.
anyone with similar experiences and what readings should I be getting before
I start using this water for water-changes.

Robin