LASCO 05-1771 Self Draining Vacuum Breaker with Fine Thread, For Arrowhead 490BPF and 480 Series Hydrants Protects drinking water from harmful contaminants, such as; pesticides, herbicides, backflow from broken pipes, etc. Allows water to drain from valve upon shutoff to protect faucet and pipes from freezing and damage Do not leave faucet open for more than 12 hours, not designed for constant pressure applications Faucet must be installed at a downward angle to ensure drainage and to prevent freezing Water from breaker will drain in a steady gentle stream for approximately 15-20 seconds after hydrant is turned off Arrowhead brand, part replacement for OEM 490BFP and 480 series hydrants