Which type of assembly is required when the risk of contamination is significant due to cross-connections?

A Reduced Pressure Zone (RPZ) assembly is specifically designed to prevent backflow and protect the potable water supply when there is a significant risk of contamination due to cross-connections. This type of assembly operates by maintaining a pressure differential that is lower than the supply pressure, ensuring that water flows in the intended direction and preventing any backflow of potentially contaminated water into the clean water supply.

The RPZ assembly features two check valves and a relief valve, which further enhances its protective capabilities by allowing any backpressure that occurs to escape rather than allowing it to enter the potable water system. This makes RPZ assemblies particularly suitable for high-risk situations, such as industrial applications or certain agricultural uses, where the potential for contamination is greater.

In contrast, other types of assemblies, while they may serve specific purposes in a plumbing system, do not provide the same level of protection against contamination. A single check valve assembly, for example, allows for some backflow prevention but does not offer the same robust safeguards as an RPZ. A purge valve assembly is typically used for draining or discharging water and does not have the same protective functions regarding backflow. Similarly, a pressure relief assembly is generally focused on relieving excessive pressure rather than addressing cross-connection risks.