Name a common type of backflow prevention device used in irrigation.

A reduced pressure zone (RPZ) assembly is a common type of backflow prevention device used in irrigation due to its effectiveness in preventing the backward flow of contaminated water into the potable water supply. This device is specifically designed to protect against both backsiphonage and backpressure conditions, which can occur during various events such as main breaks or sudden changes in pressure.

The RPZ assembly consists of two check valves and a pressure differential relief valve that allows for the discharge of water if the pressure drops below a specific threshold. This mechanism helps maintain a safe separation between the irrigation system and the potable water source, ensuring that any contaminants in the irrigation water do not enter the drinking water supply.

In contrast, while other options like pressure vacuum breakers and double check valve assemblies also serve as backflow prevention devices, they can be limited in certain situations compared to an RPZ assembly. Pressure vacuum breakers do not provide protection under backpressure conditions, and double check valve assemblies might not be suitable for high-risk situations where a high level of protection is necessary, which is where RPZ assemblies excel. An isolation valve, while important in irrigation systems for controlling water flow, does not function as a backflow prevention device.