What is the primary use of a pressure tank in fire protection systems?

The primary use of a pressure tank in fire protection systems is to supply water using air pressure. This system works by utilizing pressurized air to force the water out of the tank when needed, thereby ensuring that fire suppression systems can deliver water efficiently when a fire event occurs. The air pressure provides the necessary force to push water through the system's piping to reach the sprinklers or standpipes, ensuring effective fire control.

The other functions, while important in certain contexts, do not primarily define the role of a pressure tank. Maintaining constant pressure is an important aspect of fire systems, but that is typically managed by pumps and regulators, not directly by pressure tanks alone. Pressure reducing devices serve a different purpose by managing and lowering excessive pressure to acceptable levels for safety and equipment protection, which is also not the primary role of a pressure tank. Storing excess water for emergencies is vital in water supply systems, but the main function of a pressure tank is to work with air pressure to deliver water when required.