What is used to maintain fire main system pressure?

The pressure regulating valve plays a crucial role in maintaining the fire main system pressure by automatically adjusting the flow of water based on the pressure reading in the system. It ensures that the pressure remains within a specified range, which is essential for the effective functioning of fire suppression systems. If the pressure falls below or rises above the desired levels, the valve opens or closes accordingly to either allow more water flow or restrict it, thus stabilizing the system pressure. This consistent pressure is vital for delivering water effectively during a fire emergency, ensuring that sprinklers and hoses work optimally to combat fires.

The other options do not primarily serve the purpose of regulating pressure in the same manner. Pneumatic pumps are designed to move fluids using compressed air but do not directly control pressure. Flow control valves primarily regulate the flow rate rather than maintaining specific pressure levels. Check valves are used to prevent backflow in a piping system, ensuring that the fluid flows in one direction, but they do not play a role in pressure regulation.