Which device is designed to vent air to the atmosphere to prevent back siphon when pressure in the line drops?

Which device is designed to vent air to the atmosphere to prevent back siphon when pressure in the line drops?

• A. Air Gap
• B. Atmospheric Vacuum Breaker
• C. Reduced Pressure Principal Device
• D. Backflow

Answer: (B)

When pressure in a supply line drops, a siphon can pull contaminated water back toward the potable supply. The atmospheric vacuum breaker is the device designed to prevent that by venting air to the atmosphere at the moment negative pressure occurs. The air inlet opens automatically, admitting air to break the vacuum, and then closes again once pressure returns, stopping backflow through siphoning. This is different from an air gap, which prevents backflow by creating a physical gap rather than venting air into the line, and from a reduced pressure principle device, which uses multiple check valves and a relief valve to handle backflow. Backflow is the general problem, not a device.

When pressure in a supply line drops, a siphon can pull contaminated water back toward the potable supply. The atmospheric vacuum breaker is the device designed to prevent that by venting air to the atmosphere at the moment negative pressure occurs. The air inlet opens automatically, admitting air to break the vacuum, and then closes again once pressure returns, stopping backflow through siphoning.

This is different from an air gap, which prevents backflow by creating a physical gap rather than venting air into the line, and from a reduced pressure principle device, which uses multiple check valves and a relief valve to handle backflow. Backflow is the general problem, not a device.