This cartridge has a large capacity and is easy and fast to replace! The amount of purified water produced by our cartridge will average about 600 gallons, but this will vary with the quality of the incoming tap water — from as much as 1,500 gallons to as little as 250. Water quality varies by geographic location and by season of the year, which means there is not one standard that can be used for all areas. Using a HydroPure Deionizer System takes the cost and guess work out of providing pure water for your batteries. It also protects the investment you have made in purchasing your batteries. The use of impure water in your batteries shortens battery life and battery run times, which only wastes money!