Is zero tds possible with RO only?

[mike31154]

Hmm, my source water shows a TDS in the mid 200's as well and my system is similar to yours, 75 GPD. RO TDS gets down to 1, occasionally 2, but I've never seen it at 0. Source water comes from a local lake and it's considered somewhat 'hard' due to the makeup. I've checked my source water both with the Dual TDS meter and a cheap handheld. There's a discrepancy of about 30 to 40 with the Dual meter having a higher reading than the handheld for source water TDS. I'm inclined to put more trust in the Dual meter, since I used both probes and they were within 1 TDS in their readings.

Did you check the source water with both probes? If not, might be worthwhile as a comparison and to instill confidence in the reading, although an accurate reading at a TDS of 280 does not necessarily translate into an accurate reading at the lower end of the scale. That certainly seems to be a concern with refractometers in many posts & threads. Pretty sure the Dual TDS meters have a calibration adjustment on them, so it may be an idea to look into that.

Or, maybe the makeup of your source water is such that the solids are readily separated, who knows. Hopefully some fellow Calgarians will check in with their experiences.