What is the most common type of centrifugal pump?

• A. Single stage pump
• B. Two stage pump
• C. Three stage pump
• D. Variable speed pump

Answer: (A)

Single-stage centrifugal pumps deliver a high volume of water at a moderate discharge pressure using one impeller. This setup matches the typical firefighting need for ample flow without requiring very high pressure, making it the standard configuration on most fire apparatus. It’s simple, rugged, easier to service and prime, and lighter and cheaper than multi-stage designs. Two-stage and three-stage pumps stack additional impellers to generate higher pressures (head) for specialized tasks like long suction runs or high-rise operations, but that added complexity, weight, and cost mean they’re used less often. Variable-speed capability can adjust output, but the fundamental distinction here is the number of stages; the single-stage arrangement remains the most common because it balances performance, reliability, and simplicity for everyday firefighting needs.