Specifications include, but are not limited to: Annual Requirements for Fire Hydrants. Fire Hydrants shall be constructed such that the main valve closes with the line pressure, and shall open by turning left (counterclockwise). The main valve opening shall be a minimum of five (5) inches and its assembly, including the drain valve assembly, shall be removable through the upper barrel assembly. The main valve seat-ring shall thread into a bronze insert located in the shoe of the hydrant or thread into a bronze drain ring located between the lower barrel and shoe of the hydrant. All bronze or brass parts, in constant contact with water, and all flow characteristics of hydrants offered and supplied shall meet or exceed the requirements of Standard C502. Hydrants shall be rated for 250 psi working pressure.