The valve body and its cover are to be made of good quality, close-grained gray cast iron, so designed and the metal so distributed as to insure strong smooth castings. They are to be hot galvanized with sufficient thickness of coating to insure a smooth unbroken surface. The valve body is to be equipped with end flanges, the size and drilling of which shall be in accordance with the American Standard for 125 pounds cast-iron pipe flanges and flange fittings as approved by the American Engineering Standard’s Committee, February, 1929. The overall length of the valve body from face of flange to face of flange shall be:

The valve body and cover, when bolted together, must safely withstand an internal working pressure of 150 pounds per square inch with a factor of safety of at least five in the three-inch, four-inch and six-inch sizes and a factor of safety of at least four in the eight-inch size.

The valve body shall be equipped with a bronze seat ring having a passage through it equal to the diameter of the pipe size for which the device is intended. The seat ring shall be firmly screwed in place with a fine thread and the working face shall be smoothly tin-coated to prevent sticking of the clapper rubber.

The hinge pins shall be made of phosphor bronze and shall be supported in the valve body in bronze bushings. Holes through the valve case for the hinge pins shall be closed with brass or bronze pipe plugs. The clapper and clapper arm shall be made of bronze composition and so arranged that they and any supplementary parts may swing clear of the main waterway through the valve case, so that there may be a clear and direct passageway therethrough at least equal in cross-sectional area to the area of the pipe size for which the device is intended.

The construction of parts must be such that the clapper will close by gravity. It shall have a supplementary weight so arranged as to exert by compound leverage and additional force on the clapper arm. The supplementary weight must be so arranged as to release this additional force upon the clapper arm immediately the valve opens.

The clapper shall be fastened to the clapper arm by means of a bronze connection in such manner that there can be no leakage at this point. The clapper must be free to swing, with relation to the clapper arm, a sufficient amount so that it will at all times be free to take a flat bearing against the valve seat.

The clapper shall be faced with a ring of medium-hard rubber backed over its entire surface by a smoothly machined surface on the clapper. It must be protected at its outer edge for at least one-third of its thickness, and the clapper rubber must overhang the seat ring by at least one-eighth inch. [Ord. 962 Art. IV, § 33, 1959; Code 1970 § 13.28.030; Code 1954 § 4-3.64.]