What is the primary function of a pressure relief valve in a plumbing system?

The primary function of a pressure relief valve in a plumbing system is to release excess pressure. This is crucial for maintaining safety and functionality within the plumbing system. If the internal pressure of the system becomes too high, which can occur due to thermal expansion, thermal overload, or malfunctioning equipment, the pressure relief valve automatically opens to allow water (or steam, in some applications) to escape. This helps to prevent damage to pipes, fixtures, and appliances, as well as reducing the risk of leaks or catastrophic failures in the system. In essence, by discharging excess pressure, the valve protects the integrity of the plumbing system, ensuring that it operates within safe limits.