Module 2 · Pumps, Level Controls, and Operating Cycles

Lead, Lag, and Alternation

The lead pump is the first pump called when the wet-well level rises. A lag pump starts when the lead pump cannot keep pace or when the level reaches another control point.

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Alternation changes which pump becomes lead for the next cycle. This can distribute run time and starts between available units. Balanced use also helps reveal whether both pumps can perform the duty.

Unequal hours do not always mean a fault. Different pump sizes, programmed sequences, maintenance outages, or peak-flow operation may create an intended difference. Compare results with the station's control description.

If a pump is unavailable, staff must understand how capacity and alternation are affected. Record the change and follow the plant's reduced-capacity and notification procedures.