A21.10-1971 (C110-71): American National Standard for Ductile-Iron and Gray-Iron Fittings, 2 In. Through 48 In., for Water and Other Liquids (PDF)

Specifications for fittings with mechanical joints, bell-and-spigot joints, and flange joints are given in the tables. This standard may also be used for fittings with push-on joints or such other joints as may be agreed upon at the time of purchase. For the 3-12 inch size range, ductile iron mechanical joint fittings as shown in the tables are rated for 350 psi working pressure, and gray iron fittings having all types of joints covered by this standard are rated for 250 psi working pressure. For the 14-48 inch size range, fittings having all types of joints covered by this standard are shown in the tables as gray iron and/or ductile iron for rated working pressures of 150 psi and 250 psi.