What device should be installed in a pump discharge line to prevent backflow during shutdown?

Installing a check valve in the pump discharge line is essential for preventing backflow during shutdown. A check valve allows water to flow in one direction—away from the pump—while automatically closing to stop any reverse flow when the pump stops running. This is crucial in maintaining system pressure and preventing contamination or damage caused by the reverse flow of water, which can occur if the system experiences a drop in pressure.

The other devices listed serve different functions. A pressure regulator is designed to maintain a specific pressure level in the system but does not prevent backflow. A water trap is primarily used to collect moisture or sediments and is not relevant to backflow prevention. A flow meter measures the rate of water flow but also does not prevent backflow. Thus, the check valve is the most suitable device for ensuring that backflow does not occur when the pump is shut off.