With my 250 Deer Run, I remove 75% in one pass, when I run a second pass I then remove about 50% more. So if I start with 2% sap (this year it's been much lower) in one pass I have about 8% concentrate and in 2 passes I'm at or near 12%. I don't try to go over 14% because the RO membranes start to plug and I need to do a cold permeate rinse for about 5 minutes before I can resume. I don't like doing that because it is adding lots of water back into the concentrate that the RO removed once already.
Pricier RO's can get more concentration. By the way, the 2 membranes are in series.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.