Priming devices on modern fire pumps most often are which type?

• A. Used to boost pump pressure
• B. Used for supply from a hydrant
• C. Positive displacement pumps
• D. Used all the time

Answer: (C)

Priming devices must create a reliable prime so the pump can draw water from a non-pressurized source. On modern fire pumps, the priming device is typically a positive displacement pump. Because this type moves a fixed amount of fluid with each cycle, it can generate a strong suction and push water into the pump casing even when starting from dry air. This makes the prime quickly and reliably established, which is essential for drafting. Once prime is established, the main pump (usually centrifugal) can develop the required pressure.

Other options describe functions or situations that aren’t about the priming mechanism itself—boosting pressure, supplying from a hydrant, or being used continuously—whereas the positive displacement priming pump is specifically the device that accomplishes the priming action.