This standard pertains to the various types and classes of wet-barrel fire hydrants for use in water-supply service in areas where the climate is mild and freezing temperatures do not occur. A wet-barrel hydrant has one or more valve openings above the ground line and, under normal operating conditions, the entire interior of the hydrant is subjected to water pressure at all times. Each outlet nozzle has an independent, compression-type valve (i.e., working with or against the pressure) that controls discharge from that particular outlet. This standard does not pertain to dry-barrel fire hydrants. (For such hydrants, see ANSI/AWWA C502, Dry-Barrel Fire Hydrants.) References to the setting of hydrants are not included in ANSI/AWWA C503. For installation information, see ANSI/AWWA C600, Installation of Ductile-Iron Water Mains and Their Appurtenances; ANSI/AWWA C603, Installation of Asbestos-Cement Pressure Pipe; and AWWA Manual M17, Installation, Field Testing, and Maintenance of Fire Hydrants. Hydrants of steel-pipe risers and angle-valve construction are not covered in this standard. Major changes made to the standard in this revision include the following: additional alloys have been included in Table 1, Copper alloys; Table 3, maximum permissible loss of head for hydrants, has been changed; the addition of references to stainless-steel components; and, Sec. 4.4.13, Gaskets, and Sec. 4.7, Coatings, have been revised.