This standard covers iron-body, resilient-seated gate valves, including tapping gate valves, with nonrising stems (NRS) and outside-screw-and-yoke (OS&Y) rising stems for water supply service. 1.1.1 Sizes. Gate valves covered by this standard are 3 in. (75 mm), 4 in. (100 mm), 6 in. (150 mm), 8 in. (200 mm), 10 in. (250 mm), 12 in. (300 mm), 16 in. (400 mm), and 20 in. (500 mm) nominal pipe size (NPS). Sizes refer to the nominal diameter, in inches (or millimeters), of the waterway through the inlet and outlet connections and the closure area. 1.1.2 Valve pressure rating. The minimum design working water pressure shall be 200 psig (1,380 kPa [gauge]) for 3- through 12-in. (75- through 300-mm) size and 150 psig (1,034 kPa [gauge]) for 16- and 20-in. (400- and 500-mm) sizes. 1.1.3 Conditions and materials not covered. This standard is not intended to cover special conditions of installation or operation, such as built-in power drive, installation in vertical or steeply inclined lines, conveyance of unusually corrosive water, or excessive water hammer. 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 C509 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; Repairs to castings of valve components have been clarified (Sec. 5.1.2.); Discussion of 16-in. (400-mm) and 20-in. (500-mm) valves has been added to the scope of this standard (Sec. 1.1.1).