WI-HP-SECURE-.75C Water Inc. HousePure Secure Replacement Cartridge Replacement Cartridge for HousePure Secure 3/4 in tankless water heater filter system. The 5-micron filter with polyphosphate scale reducing media provides consistent flow rates and superior filtration performance.The HousePure Secure cartridge should be changed annually or when gauge indicates a change is needed sooner.Capacity: One year or when gauge indicates change neededDimensions: Height: 20 in Diameter: 2.5 inTested to NSF/ANSI Standard 42 for material requirements.