Butterfly valves shall be A.W.W.A. cast iron body with bronze retainer rings per A.W.W.A. specification C-504, Class 150B with hydrostatic test pressure of 300 psi. Such valves shall be installed on all mains 12 inches or greater in diameter at those points in the system as may be designated by the Village Engineer so as to sectionalize the mains into reasonable divisions. All butterfly valves shall be installed in valve vaults as set forth in § 50.075, and shall be equipped with ground-level indicators at the time of final inspection.