Carbon filters require very little maintenance, and are perhaps the most powerful chemical absorbents known to man. bobble's carbon-based filter removes organic contaminants from regular municipal tap water and meets or exceeds the NSF International Standard 42 for chlorine, taste and odor reduction. For best results we recomment changing your filter after 2 months or 40 gallons/150litres. Filter for use with bobble only WARNING: Do not use where water is microbiologically unsafe or of unknown quality.