Abstract: A tri valve backflow preventer having parts and materials preferably consisting of steel nuts and bolts, ductile iron operating nuts, nitrile rubber O-rings, nitrile rubber gaskets, manganese bronze valve adjusting stems, valve wedge gates made of ductile iron encapsulated with EPDM rubber, and ductile iron valve bodies. Material and parts are constructed in accordance with ASTM standards and the requirements of the AWWAC-509 and AWWAC-504 for gate valves and butterfly valves. The tri valve backflow preventer is used with a temporary conventional backflow assembly between existing water main pipe and new/upgraded sections of water main pipe while they are under construction. It is left in place when the temporary backflow assembly is removed. Its use saves extra inspection hours, extra man hours, extra equipment hours, conserves large amounts of good water otherwise needed for flushing, and reduces the safety risk to the public during activation of new water lines.