What is the function of a discharge pressure relief device in an NFPA 20 system?

• A. To protect the system from overpressure by venting excess discharge pressure
• B. To regulate discharge temperature
• C. To measure discharge flow rate
• D. To provide additional discharge capacity during peak demand

Answer: (A)

The main idea is safety against overpressure on the fire pump discharge. A discharge pressure relief device opens when the discharge pressure would rise above a safe limit, venting excess pressure to prevent damage to the pump, piping, and components downstream. It’s set to a predetermined relief pressure and stays closed under normal operation, then vents to a safe location (often to the atmosphere or a designated safe path) until pressure drops back to normal. This is especially important if a downstream valve is closed or a discharge path is blocked, which could cause the pump to generate excessive pressure. It doesn’t regulate temperature, measure flow, or add capacity during peak demand; its purpose is to protect the system from overpressure by relieving the excess discharge pressure.