Which of the following is NOT a main factor influencing discharge pressure?

• A. Amount of water being discharged
• B. Speed of impeller
• C. Incoming water pressure
• D. Area of discharge valve

Answer: (D)

Discharge pressure is mainly set by the pump’s ability to develop head against the system and the demand placed on the system. If you push more water through the system, the pump must generate higher pressure to overcome friction and elevation losses, so discharge pressure rises with flow demand. Pushing the pump faster (increasing the impeller speed) increases the head the pump can produce, raising discharge pressure for the same system. Having higher incoming water pressure at the suction helps the pump deliver higher discharge pressure because the net head the pump has to create is reduced. The area of the discharge valve is not a primary factor in determining the pressure the pump generates; it mainly controls how much flow the system will accept and how the system resistance changes, which can alter the operating point but does not set the discharge pressure by itself.