When the system flips over, replace the SmartChlor Cartridge by rating the two cartridges until the arrows align and pull apart. Drain the water from the old SmartChlor Cartridge and shake slightly to see if it is empty. Follow disposal directions and replace what a new SmartChlor Cartridge. Do not discard or recycle cartridge if a small amount of chlorine remains. Place in hot tub to float on its own until completely empty.