Final answer:
The pressure control valve reduces the system pressure to a lower level during the Type III hydrant system's shut down process.
Step-by-step explanation:
During the Type III hydrant system's shut down process, the pressure control valve reduces the system pressure to a lower level.
For example, let's say the initial system pressure is 100 psi. During the shut down process, the pressure control valve may reduce the system pressure to a target level of 20 psi.
By reducing the pressure, the system becomes safe to work on or maintain without the risk of high-pressure water causing any damage.