All thermoplastic check valves shall be True Union Ball type constructed from PVC Type I, ASTM D1784 Cell Classification 12454 or CPVC Type IV, ASTM D1784 Cell Classification 23447. All O-rings shall be EPDM or FKM. All valve union nuts shall have Buttress threads. All valve components shall be replaceable. All EPDM valves shall be certified by NSF International for use in potable water service. All 1/2 to 2 in valves shall be pressure rated at 235 psi and all 2-1/2 to 6 in and all flanged valves shall be pressure rated at 150 psi for water at 73 deg F, as manufactured by Spears® Manufacturing Company.