What degree of hazard does a dual check valve type backflow preventer protect against?

A dual check valve type backflow preventer is designed to protect against low hazard scenarios in plumbing systems. This type of device is typically used in applications where the potential for contamination is minimal, such as in residential water supply systems or irrigation systems that do not involve substances that could cause significant harm if introduced into the drinking water supply.

The dual check valve operates by utilizing two separate check valves within the assembly, which act as barriers to prevent backflow. This configuration effectively mitigates the risks associated with low hazard connections, ensuring that non-hazardous fluids do not migrate back into the potable water supply.

In contrast, higher hazard conditions, such as those involving toxic or corrosive substances, require more robust protection measures, such as an air gap or a reduced pressure zone assembly. Therefore, while the dual check valve is adequate for preventing backflow in low hazard applications, it is not suitable for situations where higher levels of risk exist in relation to water quality and safety.