What type of hazard does RPZ protect against?

The correct choice is centered around the primary function and design of a Reduced Pressure Zone (RPZ) backflow preventer, which is specifically engineered to protect against high health hazards. In the context of cross-connection control, high health hazards refer to situations where contaminated water could enter a potable water supply, posing serious health risks to individuals consuming that water.

RPZs use a dual check valve system with a pressure differential, which maintains a lower pressure in the zone between the check valves. This design is crucial because it ensures that even if there is a drop in water pressure in the system, contaminated water cannot flow back into the clean water supply. This mechanism is essential for environments where the consequences of contamination could lead to severe health implications, such as in hospitals, chemical facilities, or agricultural settings.

Understanding the specific context of hazards is important. Non-health hazards involve situations that may cause discomfort or nuisance but do not pose a direct health threat, while physical hazards and environmental hazards have different implications that do not directly involve the health safety of drinking water. Therefore, recognizing that RPZs are specifically designed to safeguard against high health hazards clarifies why this answer is the most appropriate in the context of backflow prevention.