This standard establishes minimum requirements for double-disc swingcheck valves, 2-in. (50-mm) through 48-in. (1,200-mm) NPS, with various body and end types for raw, potable, and reclaimed water having a pH range from 6 to 12 and a temperature range of 33-125°F (0.6-52°C). Body types. Valves described in this standard are provided with wafer or threaded-lug ends for installation between ANSI Class 125 flanges or grooved ends for use with IPS pressure pipe. Gray-iron pressure ratings. The minimum design working water pressure for gray-iron valves shall be 200 psig (1,380 kPa) for 2-in. through 12-in. (50-mm through 300-mm) NPS inclusive and 150 psig (1,030 kPa) for 14-in. through 48-in. (350-mm through 1,200-mm) NPS inclusive. Ductile-iron pressure ratings. The minimum design working water pressure for ductile-iron valves shall be 250 psig (1,720 kPa) for 2-in. through 48-in. (50-mm through 1,200-mm) NPS inclusions. Fluid velocity rating. The maximum fluid velocity shall be 16 ft/s (4.9 m/s). Installations. Double-disc swing-check valves are designed for installation in horizontal pipelines and in vertical lines with flow in the upward direction. Valves must be installed with hinge pins in the vertical position for horizontal pipeline installations. Excepted conditions. Conditions of water hammer, hydraulic pulsation, and excessive noise are beyond the scope of this standard and require special design and construction consideration. Major changes made to the standard in this revision include the following: the title of the standard was revised to Double-Disc Swing-Check Valves for Waterworks Service, 2-in. Through 48-in. (50-mm Through 1,200-mm) NPS, an advisory statement was added in the Foreword (Sec. II.C) regarding chlorine and chloramine degradation of elastomers, permeation (previously Sec. 4.1) was moved to an advisory statement in the Foreword (Sec. II.D), revised the ASTM A536 material requirements. added aluminum bronze as an optional pin material, and