What is an acceptable means of backflow prevention?

A barometric loop is an effective method to prevent backflow, particularly in situations where high levels of backpressure could occur. This system utilizes a vertical rise in the piping, allowing fluid to flow freely under normal conditions but preventing reverse flow due to changes in pressure or vacuum conditions. The elevation creates a physical barrier that helps protect the drinking water supply from contamination, making it a reliable option for preventing backflow, especially in specific installation scenarios.

While the other choices also represent various backflow prevention methods, they serve different functions, and their effectiveness can depend on specific applications and circumstances. Each has its own limitations and may not be suited for all situations, hence the barometric loop stands out in contexts requiring resistance to backpressure in elevated systems.