This standard describes the various types and classes of cold-water displacement meters with plastic main cases, in sizes 1/2 in. (13 mm) through 1 in. (25 mm), for water utility customer service, and the materials and workmanship employed in their fabrication. The displacement meters described, known as nutating-disc or oscillating-piston meters, are positive in action because the pistons and discs displace or carry over a fixed quantity of water for each nutation or oscillation when operated under positive pressure. Major revisions made to the standard in this edition include the following:
a section on fire flow service has been added to the foreword (Sec. II.B); updated AWWA materials language has been added (Sec. III.A.3 and Sec. 4.1); metric equivalents for 5/8 in. meter size has been corrected; a note on test details for 1/2-in. and 1/2-in. x 3/4-in. meters has been added (Sec. B.2.3); and, the relaxation for test intervals for magnetic couplings has been removed (Sec. B.5.1).