In a lift station, which observation would most strongly indicate the lead pump is air-bound?

• A. Lag pump is closed
• B. Lag pump is air-bound
• C. Lag pump is air-bound
• D. Lead pump check valve stuck open

Answer: (A)

Air binds in a lift station when air is trapped in the suction line, preventing the lead pump from priming and moving liquid. In a two-pump setup, the control sequence is designed so that the lag pump only runs when the lead pump is delivering flow. If the lead pump is unable to move water because it’s air-bound, the system won’t start the lag pump, so the lag pump remains closed. That lack of lag-pump operation, despite rising liquid levels, is the strongest clue that the lead pump isn’t pumping due to an air-bound condition. The other observations would point to problems with the lag pump itself or a different fault, not specifically the lead pump being air-bound.