Alabama Contractors License Practice Exam

What should relief valves installed on water heaters be set to open above the operating pressure?

1. 25 psi

2. 50 psi

3. 75 psi

4. 100 psi

The correct answer is: 75 psi

Relief valves on water heaters are crucial safety devices designed to prevent excessive pressure buildup inside the tank. These valves open to release water and reduce pressure when it exceeds a predetermined limit, ensuring that the water heater operates safely within its recommended pressure range. Setting relief valves to open at 75 psi is appropriate because it typically aligns with the operating pressures of residential water heating systems. Most standard residential water heaters are designed to operate at a maximum working pressure of around 60-80 psi. Therefore, setting the relief valve to open at 75 psi provides a safety buffer, preventing the possibility of dangerous over-pressurization while ensuring that the system remains effective during normal operation. Choosing a lower pressure setting, such as 25 or 50 psi, might result in frequent trips of the valve, causing unnecessary water loss and reducing the efficiency of the system. Setting it at 100 psi could lead to the danger of excessive pressure buildup leading to possible rupture or catastrophic failure of the water heater. Thus, 75 psi strikes a balance between safety and operational efficiency, making it the ideal choice for relief valves in water heaters.