A fluid hydrant has an outlet with a threaded outer surface, and a backflow preventor is mounted on the inlet of the hydrant. The backflow preventor has an inlet and outlet end. Male hose threads are formed on the exterior of the outlet end of the backflow preventer. Interior female threads are on the inlet end thereof. A bushing adapter is interposed between the inlet end of the backflow preventor and the threaded nozzle of the hydrant with the threads connecting the adapter and the backflow preventor being of a size different than the threads connecting the adapter and the threaded nozzle of the hydrant. The bushing adapter extends over the threaded outer surface of the outlet of the hydrant, and a locking cement between the threaded outer surface of the outlet of the hydrant and the interior female threads on the inlet end of the bushing adapter rigidly fix these threads together. The method permanently affixing a backflow preventor to the threaded outer surface of a hydrant comprises taking a backflow preventor having an inlet end with a threaded interior; threading an adapter between the inlet end of the backflow preventor and the threaded outlet of the hydrant; providing different thread sizes at the interior and exterior surfaces of the adapter, with the threads at the interior surface being compatible with the threads of the nozzle on the hydrant; and placing a locking adhesive between the interior threads of the adapter and the nozzle threads of the hydrant.