Final answer:
Discharge piping serving a pressure-relief valve must have a backflow preventer to maintain system safety and integrity.
Step-by-step explanation:
Discharge piping serving a pressure-relief valve shall be provided with a device designed to prevent backflow. In systems where pressure relief is critical for safety, such as in boilers or pressure vessels, the discharge pipe is often fitted with mechanisms that ensure the expelled fluids or gases do not re-enter the system. These devices are crucial in maintaining the integrity of the pressure-relief pathway and in protecting the system from potential damage due to backflow. Common backflow preventer systems include check valves or vented loops, which are designed to only allow flow in one direction, thereby preventing any reverse movement that could compromise the system's safety.