Which backflow preventer is not suitable for continuous pressure situations?

The atmospheric vacuum breaker is designed to prevent backflow in situations where a negative pressure occurs, thus ensuring that potable water does not become contaminated by back siphoning. However, it is not intended for continuous pressure situations because it relies on atmospheric pressure to function properly. When there is constant pressure in the system, the mechanism cannot operate as intended.

In contrast, backflow preventers like the air gap, pressure vacuum breaker, and double-check valve can manage continuous pressure effectively. An air gap physically separates the water supply from contaminated sources and is not influenced by pressure conditions. A pressure vacuum breaker can maintain its function under continuous pressure, making it suitable for more demanding systems. Similarly, a double-check valve is designed to provide reliable protection against backflow under constant pressure conditions.