Turn off the water supply to the housing unit. Press the red pressure relief button to relieve pressure and unscrew bowl counter clockwise. Discard old cartridge. The "O" ring in the housing should be inspected and lubricated as necessary. Remove outside wrapper from the new cartridge and install in bowl.  After installation, filter should be flushed with sufficient water to remove any traces of fines. Under normal circumstances, treatment will last for up to six months. Date this canister upon installation and replace it in six months.  This filter should not be used where the water is microbiologically unsafe or with water of unknown quality without adequate disinfection before and/or after the filter.