I suggest you mix in the preservative. My method would be to add it to the wash tank and circulate it thru the membrane(s) for 5 minutes. Then shut the RO off. Now, if you want to store the membrane(s) in PVC containers, remove them from the RO, and place in the PVC tubes, then top off the level in the container to about 1" low and close, then in a few days, open the tube, top off the mixture (from the wash tank) again to be about 1" low, close and store until next year. Then drain the RO wash tank, pump and all parts that have liquid in them and then prepare for next season a few days ahead of the season, put the membranes in the RO, run the before the season regimen and keep the RO from freezing. Do not use chlorinated water or hard well water.
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.