🔍 Key Concepts

• Pressure relief valves on fire main systems protect piping and hoses from excessive pressure • Relationship between required operating pressure at hydrants and the relief valve setting • Safety margins typically added above normal operating pressure so demand can be met without lifting the relief valve

💭 Think About

• If the pump must deliver 175 psi to get 50 psi at the two highest hydrants, what happens if the relief valve is set too close to 175 psi? • If the relief valve is set too high, what risk does that create for hoses, fittings, and personnel using the fire main? • Which choice allows the system to build enough pressure to meet the hydrant requirement, but still limits maximum pressure to a safe value above normal operating pressure?

✅ Before You Answer

• Confirm the pump’s required discharge pressure (175 psi) is the pressure you must be able to reach before the relief valve starts to open • Check which answer choices are higher than 175 psi, since the relief valve must not open during normal operation • Verify that the chosen setting leaves a reasonable safety margin above 175 psi without being excessively high for typical fire main components