Which type of intake pressure may centrifugal fire pumps use?

• A. Negative intake pressures
• B. Positive intake pressures
• C. Atmospheric intake pressures
• D. Vacuum intake pressures

Answer: (B)

Centrifugal fire pumps work best when water enters the impeller under positive pressure. When the intake side is pressurized by a connected water source like a fire hydrant or another pressurized supply, water is pushed into the pump, helping maintain a strong, consistent flow and reducing the risk of cavitation and prime loss. If the intake were negative or a vacuum, air could be drawn into the pump, starving it of water and causing cavitation or loss of prime. While atmospheric intake pressure can occur, it offers less margin for high-demand pumping and increases the chance of air entry under heavy flow. So, the most effective and practical condition for a centrifugal fire pump is a positive intake pressure.