Most water pitchers use granular-activated carbon and resins to bond with and trap contaminants. These filters are effective at improving the taste of water, and many will also reduce lead and other contaminants. Specific contaminants removed vary by model and depend on the pore size and other factors. An activated carbon filter, by itself, is not designed to remove all disease-causing organisms. Carbon filters have a specified shelf life and should be replaced regularly according to the manufacturer's instructions. Filters that attach to a faucet or are installed under the sink for a drinking water third faucet generally use the same technologies as their pour-through pitcher counterparts. Some filters use fabrics, fiber, or ceramic screening to physically remove contaminants. The most common types use a molded block of activated carbon. These filters are effective at improving the taste of tap water, and some will also reduce lead, protozoan cysts, and many other contaminants. Like filter pitchers, shelf lives and specific contaminants removed vary so read the label and instructions carefully. Additional information on filters is available in Water Health Series: Filtration Facts available at http://www.epa.gov/sites/production/files/2015-11/documents/2005_11_17_faq_fs_healthseries_filtration.pdf.
EPA neither endorses nor recommends specific home water treatment units. No single unit takes out every kind of drinking water contaminant; you must decide which type best meets your needs. For help in picking a unit, contact one of the following independent non-profit organizations: NSF International (800-673-8010), Underwriters Laboratories Inc. (888-547-8851) Water Quality Association (630-505-0160). Both NSF International and Underwriters Laboratories Inc. test and certify home water treatment units. The Water Quality Association classifies units according to the contaminants they remove as well as listing units that have earned their Gold Seal approval. Water treatment units certified by these organizations will indicate certification on their packaging or labels.