1.RV VACUUM BREAKER CHECK VALVE: Suitable for BB 571 check valves which are part of a black water tank flushing system and are installed between the fresh water inlet and the tank flusher. The vacuum breaker can help prevent black tank water from mixing with grey water to ensure clean and y water 2.D CONSTRUCTION: This 571VACCHKA RV Vacuum Breaker Check Valve is made of brass and can withstand 8125 PSI of water pressure. Less susceptible to zing and cracking in cold climates, better performance and longer life than plastic 3.EASY INSTALLATION: Can simply be fitted to a caravan's black water tank flushing system and must be installed 6' above the highest point of any item connected to the waste water tank where the flusher is fitted. If installation assistance is needed, it is recommended to consult a professional plumber 4.VERSATILE APPLICATION: This vacuum breaker check valve is suitable for all models of caravans, campers, preventing the contents of the black water tank from siphoning back into the RV freshwater system, travel trailers and motels and is a reliable alternative to ruptured or leaking check valves