Cash Acme V-3 Series hose bibb atmospheric backflow preventer with a 3/4" NPT male connection. This backflow preventer/vacuum breaker is designed to prevent dangerous back-siphonage and backflow into a potable water supply. Its maximum pressure is 125 psi and it has a maximum temperature is 180°F. The V-3 features all-brass construction with threaded connections, a neoprene seat disc, rubber washer, and steel set screw. The V-3 is equipped with a protruding tip device for manual draining of faucet (after hose removal) which prevents freezing. These units are not intended for use where water contamination could occur as a result of draining or for permanent continuous pressure installation. For continuous pressure systems, install a BFP Series backflow preventer valve instead. V-3 Series backflow preventers are for use around homes, schools, commercial buildings, laboratories, and any place involving moveable hoses that are attached to threaded faucets, indoors or out. The V-3 attaches to any standard male 3/4" hose-thread sill cock. The valve is fitted with a male outlet connection to permit garden hose attachment. When backflow conditions occur, due to back pressure or back-siphonage, the seat and diaphragm close to prevent any water from flowing back through the unit and into the water supply line. At the same time, the diaphragm lifts off the vent holes to break any vacuum, and any trapped water under pressure is allowed to escape through the vent holes.