Which statement best describes the effect of higher drafting altitude on pump operation?

• A. Drafting altitude has no effect.
• B. Higher altitude improves air intake.
• C. Lower altitude worsens pump performance.
• D. Higher altitude can reduce atmospheric pressure and influence air intake; adjust operations accordingly.

Answer: (D)

Drafting relies on atmospheric pressure to push water into the pump via the suction line. The pump creates suction on the intake side, and the amount of water you can lift is limited by the surrounding air pressure. As you gain altitude, atmospheric pressure and air density fall, so the maximum suction lift you can achieve decreases. If the water source is too far below the pump or the suction path has extra friction, the pump may lose prime or draw in air, leading to reduced flow and possible cavitation. Because of this, at higher drafting altitudes you need to adjust how you approach drafting—prefer a source closer to the water surface or at a lower elevation, minimize suction line losses, and ensure proper priming and air removal so you maintain prime and adequate flow. That’s why the statement notes that higher altitude can reduce atmospheric pressure and influence air intake, and that you should adjust operations accordingly.