After I've done a soap wash, I've cycled permeate through the wash tank to get the tank clean. At the end of the season, I'll be cycling preservative through the membrane, but there won't be a rinse that follows it - until next year. The residue of the preservative will be in the wash tank. I can't rinse it out, because the drain from the wash tank goes right into the pump and membrane.
How do others clean out their wash tank for the last time in a season? Is it okay to just let the tank sit with the preservative dried in there?