If a pump operating at 700 kPa from its tank is connected to a hydrant with a pressure of 350 kPa and the relief valve is not set, the maximum discharge pressure of the pump will be:

• A. 700 kPa
• B. 350 kPa
• C. 1050 kPa
• D. 1400 kPa

Answer: (C)

The pressure at the pump discharge is the sum of what the water already has on the suction side plus what the pump adds as it pushes the water into the discharge system. In this scenario, the water coming from the tank is at 700 kPa, and the hydrant system presents a back pressure of 350 kPa. With no relief valve set to vent excess pressure, the pump must push against that back pressure, so the discharge line reaches 700 kPa plus 350 kPa, totaling 1050 kPa. If a relief valve were present and set, it would limit the maximum discharge pressure to that valve setting, preventing the pressure from reaching the full sum.