The operation in which each impeller of a multi-stage centrifugal pump discharges into a common outlet is known as:

• A. Parallel
• B. Series
• C. Pressure
• D. Single Stage

Answer: (A)

This configuration is parallel. When multiple impellers discharge into a common outlet, their flow rates add together in the discharge path, so the total output flow is the sum of each impeller’s flow. The pressure (head) produced at the common discharge remains roughly what a single impeller would produce at the same shaft speed, rather than increasing with each stage. If the impellers were arranged in series, the flow would pass from one stage to the next to raise head, not sum at a common outlet. A single-stage pump uses only one impeller, so having multiple impellers discharging into a common outlet indicates parallel operation.