Increased pump vacuum and increased run time for one of two pump stations' centrifugal pumps is MOST likely caused by:

• A. Phase-to-phase voltage imbalance
• B. Failed pump bearing
• C. Increased flow to the station
• D. Suction line has become clogged

Answer: (D)

When a suction line becomes clogged, the pump has to pull water through a restriction on the intake. That adds friction losses on the suction side and creates a larger negative pressure (vacuum) at the pump inlet. Because the flow is now restricted, the pump can’t deliver as much water as before, so the station has to run longer to meet demand. This combination—higher suction vacuum plus longer run time for that one station—points to a suction-side blockage.

In contrast, a phase-to-phase voltage imbalance would tend to affect motor performance more broadly and isn’t tied to suction-side restrictions; a failed bearing would show up as unusual noise or vibration and mechanical issues rather than a sudden suction vacuum increase; and simply increasing flow to the station wouldn’t necessarily produce higher suction vacuum at the pump inlet.