Which of the following is a commonly used backflow protection device in cold water systems?

• A. Filter.
• B. Reduced Pressure Zone (RPZ) assemblies.
• C. Pressure gauge.
• D. Ball valve.

Answer: (B)

Reduced Pressure Zone assemblies are a commonly used backflow protection device in cold water systems. They prevent contamination by stopping any reverse flow from entering the potable supply. The unit uses two check valves separated by a space and a relief valve that vents to the drain if pressure on the supply side drops. This creates a reduced pressure area that blocks backsiphonage and backflow, keeping the drinking water safe even when a downstream cross-connection tries to draw water backward. They’re favored in many cold-water installations because they provide high-level protection against both backsiphonage and backpressure and are designed to handle varying pressures and higher-hazard connections, with codes often requiring them in specific applications like irrigation with fertilizers or boiler make-up lines. The other options don’t provide reliable backflow protection: a filter cleans particulates but won’t stop reverse flow; a pressure gauge only measures pressure; a ball valve can shut off flow but doesn’t prevent backflow or vent to drain and thus doesn’t meet backflow protection requirements.