WD-K19RF Filter for Waterdrop K19 Countertop Reverse Osmosis SystemModel WD K19RF Adaptive Model WD K19 S Material PP cotton, carbon block, RO Membrane Filter life Up to 12 months or 1,000 gallons What will happen if my filter has expired and I dont change the expired filter? Over used filters will degrade the filtration performance, causing contaminants to leak back into the water and adversely affect your health. It is recommended to replace the filter on time. How often do I need to change the filter? The filter