The RP (Reduced Pressure) device is the most reliable backflow if an air gap is not in place

• A. RP (Reduced Pressure)
• B. Air Gap
• C. Double Check
• D. Atmospheric Vacuum Breaker

Answer: (A)

Backflow prevention aims to keep contaminated water from flowing back into the potable supply. If an air gap isn’t possible, the Reduced-Pressure (RP) device offers the strongest protection among common backflow preventers. It combines two independent check valves with a relief valve that creates and maintains a reduced-pressure zone. If conditions try to push water backward, the relief valve vents to the clean side, so backflow is blocked even if a check valve leaks. This redundancy and active venting handle both backpressure and back-siphonage more effectively than other options. An atmospheric vacuum breaker can fail under backpressure or a blocked vent and isn’t suitable for continuous pressure; a double-check valve assembly provides protection but lacks the relief/venting capability of an RP device. Thus, when an air gap isn’t in place, the RP device is the most reliable choice.