Piston Activated Frost Proof Self-Draining Hose Bibb Vacuum Breaker | Lead-Free, Solid Brass 

Designed for use on yard hydrants, and hose bibbs to prevent back siphoning of contamination in the potable water supply. This self-draining Lead Free hose bibb vacuum breaker will automatically drain when the hose is disconnected from valve outlet. This is accomplished when the hose is disconnected, by causing a spring loaded plunger to spring forward off the seat, thereby allowing drainage of the valve and yard hydrant outlet. Air is now allowed in the hydrant to allow drainage and freeze protection. Draining protects the valve from freezing and rupturing in cold weather. Comes complete with a breaking set screw. Once tightened set screw will break off to prevent tampering and removal. Please note that once secured the hose bibb vacuum breaker will not be able to be removed without force by any individual.