What type of backflow prevention device is suitable for direct connections between two separate potable water systems?

The most suitable backflow prevention device for direct connections between two separate potable water systems is a double check valve. This type of device utilizes two independently acting check valves to prevent backflow from one system into another. It is specifically designed to protect against backpressure and backsiphonage, making it effective in situations where the potential for contamination exists due to interconnections between systems.

In scenarios where two potable water supplies are directly connected, using a double check valve ensures that if pressure fluctuations occur, the device will prevent any reverse flow that could introduce contaminants into a clean water supply. This makes it an appropriate choice for many applications in water distribution systems.

While other options like air gaps and reduced pressure zone backflow preventers also serve crucial roles in backflow prevention, they are typically utilized in different contexts. An air gap requires a physical separation, which may not be feasible in direct connections, and a reduced pressure zone backflow preventer, while effective, is often used in more critical situations where there is a high risk of contamination. Pressure vacuum breakers are generally used for specific applications such as irrigation systems, not direct interconnections of potable systems.