What backflow device is used when effluent is used in the irrigation system?

• A. Reduced Pressure Principle Backflow Preventer
• B. Double Check Valve Assembly
• C. Atmospheric Vacuum Breaker
• D. Pressure Vacuum Breaker

Answer: (A)

Effluent irrigation creates a cross-connection risk with the drinking water supply, so the backflow device must stop both back-siphonage and backpressure. The Reduced Pressure Principle Backflow Preventer is designed for this high-hazard situation. It uses two check valves plus a relief valve to create a reduced-pressure zone; if pressure tries to reverse, the relief valve vents to prevent any contaminated effluent from reaching the potable supply. That strong protection is why codes typically require an RPZ for reclaimed water irrigation, and it’s the most reliable choice when effluent is involved. The other devices don’t provide the same level of protection in this scenario: a double-check assembly is lower-hazard protection, and atmospheric or pressure vacuum breakers rely on vents and can’t handle backpressure or reclaimed-water conditions.