Granular Activated Carbon (GAC) generally is an organic carbon filtration media of wood, coconut shells and coal. GAC used for water purification. GAC can remove certain chemicals, particularly organic contaminants from water as well as chemicals that produce odors or tastes to water such as hydrogen sulfide or chlorine. Other chemicals, specifically iron and nitrate, can not be removed with GAC. Also GAC should be changed based on contaminant levels and water use as higher levels or use may require more frequent change-outs. Granular Activated Carbon Products range from the size 0.2mm to 4mm. Granular Activated Carbon has relatively larger particles size compared to powdered activated carbon and consequently, presents a smaller external surface.