Bill,
Dick has the right idea, given there is no safe way to winterize a reverse osmosis filter unit using propylene glycol in your coach. In some cases, depending on the type of membrane you have, propylene glycol could damage the membrane, If you decide to remove the unit and store it in a warm place, care needs to be taken to maintain a water seal so that the R.O. membrane remains saturated with water that is clorine and bacterial contamination free. I would install a shut off valve on the incoming line to the filter assembly (I think it is red) and one in the blue line which exits the R.O. filter.
Once those valves are in place run water to clear any air, shut off the valves, and then remove and store the unit. The carbon pre filter removes the clorine that will damage the R.O. membrane and you should be fine storing it as is. There is a small chance that the R.O. unit could become an incubator over the winter without a biocide in it. If the flow, color, smell, and taste is all normal on start up then you should be O.K. If not, remove the filters, disinfect the unit with a clorine solution, flush it and install all new filters. Hope this helps.
Later Ed
