What is the minimum required backflow protection?

• A. Double check Valve assembly
• B. Pressure Vacuum Breaker
• C. Atmospheric Vacuum Breaker
• D. Reduced pressure principle back flow preventer

Answer: (C)

Preventing backflow into the drinking water supply is the goal. An atmospheric vacuum breaker provides the minimum level of protection by stopping back-siphonage. It works by venting to the atmosphere and allowing air into the line whenever downstream pressure drops, which breaks any siphon that could pull irrigation water back into the supply. For many typical residential irrigation setups, back-siphonage is the main concern, and the AVB is the simplest, least expensive device that still meets the basic requirement to keep potable water safe.

Keep in mind that AVBs only protect against siphonage, not backpressure, so in systems where backpressure or higher hazard cross-connections could occur, more protective devices (like double-check valves or reduced pressure principle backflow preventers) are required. The AVB must be installed after the last downstream outlet, with the vented element positioned to stay above the highest downstream outlet and away from freezing temperatures.