A pressure-restricting device is designed to reduce pressure under which conditions?

A pressure-restricting device is specifically designed to manage the pressure of water in a standpipe system, particularly during periods when water is flowing. In watering systems, flowing conditions refer to the situation where water is actively moving through the pipes due to a discharge from a hose or other outlet. Under these conditions, the pressure can often exceed safe operational levels. The pressure-restricting device functions to lower this pressure to safe limits, ensuring that the water can be delivered effectively without causing damage to the system or posing a risk to users.

Under static conditions, which occur when no water is flowing (such as when all outlets are closed), the pressure remains constant and is typically higher. Pressure-restricting devices do not alter pressure during these static periods because there is no demand for water flow. Therefore, their primary role is realized when water is actually flowing through the system. This is why the correct understanding focuses on the functionality of the device in flowing conditions, ensuring optimal operation and safety.