The Mobile Deionizer System is designed to bring pure, battery-ready water right to where you need it. Each system uses two cartridges, which are each rated for 600 gallons (2400 liters) of pure water to provide extra deionization capacity. Only one cartridge is used at a time; when it becomes exhausted you simply turn the handle to activate the second cartridge. You can replace the exhausted cartridge when it is convenient to do so. Included purity light tells you when the cartridge is exhausted and needs to be replaced.