Designed to meet the requirements of, and are listed by the National Sanitation Foundation (NSF) under ANSI/NSF Std 61 * The Butyl diaphragm has seamless construction and is designed to flex rather than stretch and crease like bladder tanks * The polypropylene liner for the water reservoir will not flake, chip, crack or peel and does not impart taste and odor to the water * Diaphragm, liner isolate water from contact with deep drawn steel domed shell - twice as strong as rolled steel shell of same thickness * A high gloss enamel finish protects tank from the elements * Well tank stores a buffer of water in case of power loss