Why is it important to avoid air on the suction side of the pump?

• A. Air causes loss of prime and loss of water supply
• B. Air improves pump efficiency
• C. Air has no effect on prime
• D. Air can cause cavitation

Answer: (A)

Air on the suction side disrupts the pump’s ability to draw water. The suction side relies on a continuous water column to create the suction draw; if air pockets are introduced, that column breaks and the pump loses prime. Once prime is lost, the pump cannot lift water from the source, so the water supply to the discharge stops, which is critical in firefighting operations. Air can also contribute to cavitation when the pressure at the impeller drops, but the immediate and most important consequence here is the loss of prime and water supply. The other options aren’t correct because air does not improve efficiency and does affect prime; while cavitation can occur, it’s a secondary consequence, not the primary reason to avoid air on suction.