Boiler pressure relief valves play a critical role in ensuring the safety and functionality of a boiler system. These valves are designed to safeguard the boiler from overpressure, which could lead to catastrophic failures. The primary purpose of a pressure relief valve is to release excess pressure when it exceeds the predefined limit, preventing potential damage to the boiler and associated components.

These valves operate based on the principle of mechanical spring tension, combined with the force exerted by the system's pressure. When the pressure within the boiler surpasses the setpoint, the valve opens, allowing steam or water to escape and lower the pressure to a safe level. Properly calibrated relief valves are essential to maintaining the optimal operating conditions of a boiler and mitigating the risk of explosions.

The selection depends on factors such as the boiler's capacity, pressure requirements, and specific application. Boiler relief valves are different than water heater relief valves. Boilers are pressure relief only and water heaters are temperature and pressure (T&P) relief valves. All boiler relief valves must be installed vertically, never horizontal as waters relief valves are installed.
Residentually Hot water boilers normally have relief pressures as follows but could be higher.