A lift station's wet well level readings are erratic with alternating high and low levels, and both pumps start and stop inconsistently. What is the most likely cause?

A lift station's wet well level readings are erratic with alternating high and low levels, and both pumps start and stop inconsistently. What is the most likely cause?

• A. Malfunctioning level control is causing pumps to run out of phase
• B. Malfunctioning level control is causing lead-lag sequence switch to be broken
• C. Malfunctioning level control is causing pumps to run constantly
• D. Malfunctioning air bubbler system is causing erratic wet well influent

Answer: (C)

The pattern of alternating high and low level readings with both pumps starting and stopping unpredictably points to the level sensing system, not just how the pumps are controlled. A bubbler-style level sensor uses air pressure to infer liquid level; if the air line, regulator, or compressor is failing, leaking, or blocked, the readings can jump around or read incorrectly. The control then sees false high/low levels and commands pumps on and off in an irregular fashion, producing the observed erratic operation. If the level control were simply driving pumps to run constantly, you’d expect a more one‑sided condition (continuous pumping) rather than alternating readings. If a lead-lag sequencing switch were broken, you’d get improper sequencing clues rather than random level fluctuations. So, a malfunctioning air bubbler system is the most likely culprit, and inspecting the air lines, valves, and regulator for leaks or failures is a good next step.

The pattern of alternating high and low level readings with both pumps starting and stopping unpredictably points to the level sensing system, not just how the pumps are controlled. A bubbler-style level sensor uses air pressure to infer liquid level; if the air line, regulator, or compressor is failing, leaking, or blocked, the readings can jump around or read incorrectly. The control then sees false high/low levels and commands pumps on and off in an irregular fashion, producing the observed erratic operation. If the level control were simply driving pumps to run constantly, you’d expect a more one‑sided condition (continuous pumping) rather than alternating readings. If a lead-lag sequencing switch were broken, you’d get improper sequencing clues rather than random level fluctuations. So, a malfunctioning air bubbler system is the most likely culprit, and inspecting the air lines, valves, and regulator for leaks or failures is a good next step.