MATTERHORN MO-6050 System Filter Change Instructions Changing Stages-1, 2, 3 Pr-Filters: {should bie changed every 6 months) 1} Tarn OFF the cold water supply to RO system by turning the handle on the feed water adapter to the right until the handle is perpendicular to the tubing. Turn OFF the tank ball valve by turning the gray handle 90 degrees until the handle is perpendicular to the tank tubing.