Which type of backflow preventer is most commonly used in irrigation systems?

The most commonly used backflow preventer in irrigation systems is the reduced pressure zone (RPZ) backflow preventer. This device is specifically designed to protect potable water supplies from contamination due to backflow, which can occur when there is a sudden change in water pressure.

RPZ devices provide a high level of protection because they have two independent check valves and a pressure differential relief valve. The air gaps created by the check valves ensure that, even in instances of backpressure or back siphonage, the water cannot flow back into the potable supply. This is particularly important in irrigation systems where fertilizers, pesticides, and other contaminants are often present, thus increasing the risk of contamination.

While other types of backflow preventers, like the air gap and atmospheric vacuum breaker, may also provide protection against backflow, they are typically not suitable for all irrigation applications, especially those that require a more robust solution. The pressure vacuum breaker does provide some level of protection but is less effective than the reduced pressure zone device under certain conditions, making RPZ the preferred choice for ensuring the safety and integrity of the water supply in irrigation systems.