Activated carbon chemically bonds with and removes contaminants from your water as it flows through the filter. Different carbon filters vary greatly in effectiveness. Some remove contaminants such as asbestos, lead, mercury and volatile organic compounds (VOCs) while others address chlorine, taste and odor. There are two basic forms: Carbon Block and Granulated Active Carbon(GAC).
Carbon Block Filters contain activated carbon that is shaped into blocks under high pressure. They are typically more effective than granulated activated carbon filters because they have more surface area to come into contact with your water. Carbon block filters are recognized by the EPA as the best option for removing chemicals like herbicides, pesticides and VOCs. Quality carbon block filters will remove chemicals, pesticides, bacteria, heavy metals, nitrate, nitrites and parasites.
GAC filters contain fine grains of activated carbon. They are typically less effective than carbon block filters because they have a smaller surface area of activated carbon to come into contact with your water. GAC filters are best for addressing chlorine taste and color.