That’s amazing considering your starting point.. I can never get mine below 8 ppm. I think you should tinker and experiment while you are in the mode. Just remember you have to add back to the water, so anything below 20ppm you are still winning the game.A positive note is that the system is filtering the water down to 0 ppm total dissolved solids according to my meter.
Do you think if I remove the de-ionizing stage, it will produce at a better ratio, but with an increase in tds? I guess I could try it.
They are just not that efficient at this entry level, if you want a 1:1 ratio, you have to shop for the high efficiency RO systems.