this seems odd, I just got a dual inline TDS meter and of course Im playing with it... I have my RODI set up into my ATO bucket with a float valve... when the float valve closes, the back pressure causes the auto-shutoff valve to turn the RO off.. typical configuration.

In normal running situations Im getting 5TDS out of my RO, but here's where I think it's a little strange. When the autoshutoff shuts the system down, the TDS starts creeping upward to around 100. once the system starts flowing again that number goes back down to 5 eventually.

Im really not sure what this could be from, unless the DI resin is leeching its leftovers back ward as the water sits there not flowing.

any ideas?