This standard includes only the aesthetic claims such as chlorine, taste and suspended particulate removal.In general, NSF 42 standards can be met with a bed of loose granular activated carbon (GAC).

GAC has long being used in water filters to remove taste and odor. Water flows around the carbon granules and taking the path of least resistance forming channel flow and hence all the carbon surface in not effectively used. The adsorption rate is slow with GAC. The other concerns of using GAC are the potential growth of bacteria in the chamber.