This standard covers iron-body, bronze-mounted, nonrising-stem (NRS) gate valves including tapping gate valves, 3 in. (75 mm) NPS through 48 in. (1200 mm) NPS, and outside screw and yoke (OS & Y) rising-stem gate valves, 3 in. (75 mm) NPS through 12 in. (300 mm) NPS, with either double-disc gates having parallel or inclined seats, or solid-wedge gates. These valves are suitable for use in approximately level settings in water systems. 1.1.1 Valve pressure ratings. The design working water pressure shall be 200 psig (1380 kPa) for valves 12 in. (300 mm) NPS and smaller, and 150 psig (1050 kPa) for valves with diameters of 16 in. (400 mm) NPS and larger. Valves for operating pressures that fall outside these limits are beyond the scope of this standard and require special consideration in design and construction. 1.1.2 Conditions and materials not covered. This standard is not intended to cover special conditions of gate-valve installation or operation, such as built-in power drive, installation in vertical or steeply inclined lines, conveyance of unusually corrosive water, excessive water hammer, frequent operation (as in filter service) or operation in a throttled position. Such conditions are beyond the intended scope of this standard and require special consideration in design and construction. Joint accessories for end connections, such as bolts, gaskets, glands, follower rings, and so forth, are not covered in this standard. The major revisions in this edition of AWWA C500 include the following: Numerous modifications to conform to current AWWA form and content have been added; The "Modification to Standard" and "Acceptance" sections have been added to the foreword. Asbestos packing and gasket materials are no longer referenced in the standard; Information on tapping valves has been added; Soft metric equivalents have been added; Definitions have been modified; The Safe Drinking Water Act 1986 Amendments reference to maximum lead content in bronze has been added; and Repairs to castings of valve components have been clarified (Sec. 4.1.2).