Question 176General Subjects - 1st Asst/Chief

The correct answer is D) the discharge valve is closed off and there is no change in the discharge pressure. When the discharge valve of a centrifugal fire pump is closed, the pump is unable to pump any water, so the discharge pressure remains unchanged. This is because the pump is not producing any flow, and the system pressure is determined by the static head, not the pump's output. The other options are incorrect because: A) Closing the suction valve would cause the pump to lose its prime and the relief valve would lift. B) Partially closing the discharge valve would cause the relief valve to lift to maintain the desired discharge pressure. C) Closing the suction valve would cause the discharge pressure to drop, not the other way around.