Which backflow prevention device includes a relief valve as part of its mechanism?

• A. Reduced Pressure Principle backflow device
• B. Double Check backflow device
• C. Air Gap device
• D. Backflow preventer with no relief valve

Answer: (A)

The device that includes a relief valve as part of its mechanism is the one known as the reduced pressure principle backflow preventer. This type contains two check valves with a small, monitored pressure zone between them and a relief valve that vents to the atmosphere. If backflow begins or the reduced pressure zone begins to rise above the downstream pressure, the relief valve opens to discharge water, preventing any backflow from reaching the potable supply. That relief valve is what distinguishes this device from the others: a double check device uses two checks but no relief valve; an air gap relies on a physical gap rather than a valve mechanism; and a backflow preventer with no relief valve isn’t a standard or functional configuration.