Which statement is true about centrifugal pumps?

• A. Centrifugal pumps do not require priming.
• B. Centrifugal pumps must be primed before operation.
• C. Centrifugal pumps are always submersible.
• D. Centrifugal pumps are used only for wells.

Answer: (B)

Centrifugal pumps need to be filled with liquid before they can reliably move water. When the pump casing and suction line are air-filled, the impeller can spin but cannot develop the suction needed to lift water from a source, so little or no flow results. Priming fills the pump with water and removes air, allowing the impeller’s action to create the pressure needed to pull water into the pump and push it onward. That’s why priming before starting is essential unless you’re using a self-priming design or a submersible configuration.

That makes the statement about priming true. The other ideas don’t hold generally: many centrifugal pumps are not submersible, so they don’t operate underwater by default; they’re used in a wide range of applications beyond wells; and while self-priming versions exist, the standard requirement is priming, not universal elimination of priming.