Performance Requirements for Vacuum Breaker Wall Hydrants, Freeze Resistant, Automatic Draining Type
|Publication Date:||1 February 2004|
These devices are to supply potable water without danger of damage to the device due to freezing & to provide protection of the potable water supply from contamination due to back siphonage or back pressure less than or equal to 3 meters (10 feet) of head pressure. The devices shall be classified as:
(a) Type A: Automatically drain the water when the water supply is shut off & the hose removed to prevent damage from freezing;
(b) Type B: Automatically drain the water with a hose removed or attached, end nozzle closed, & the hydrant valve closed; &
(c) Type C: Same as Type A. Backflow prevention is achieved by alternate principle of holding pressure versus relieving pressure.