At 150 psi net pump pressure, the pumping system must deliver what percentage of rated capacity?

• A. 70 percent of rated capacity at 200 psi
• B. 50 percent of rated capacity at 250 psi
• C. 80 percent of rated capacity at 180 psi
• D. 100 percent of rated capacity at 150 psi

Answer: (D)

The flow rating is defined at a standard net pump pressure, typically 150 psi. That means the pump’s advertised capacity (the rated GPM) is the amount it can deliver when the discharge pressure is 150 psi. So, to meet the rating under test conditions, the pumping system must deliver 100 percent of its rated capacity at 150 psi net pump pressure. As you increase the discharge pressure beyond 150 psi, the pump’s flow naturally drops along its performance curve, so it wouldn’t be delivering full rated capacity at higher pressures. The other options describe lower fractions of flow at higher pressures, which doesn’t align with how the rating is defined.