In a rainfall-affected lift station, the most likely valve issue causing rapid lag pump cycling is which option?

In a rainfall-affected lift station, the most likely valve issue causing rapid lag pump cycling is which option?

• A. Check valve on lag pump is clogged
• B. Lag pump check valve stuck closed
• C. Lead pump check valve stuck closed
• D. Check valve on lead pump clogged

Answer: (A)

Two-pump lift stations rely on check valves to keep discharges isolated when a pump isn’t running. In rainy conditions, the wet well level can swing quickly, so the lag pump should come on and off as needed without causing the water to flow back into the well. If the lag pump’s discharge check valve is clogged, backflow from the discharge line can seep back into the wet well when the pump is supposed to be off. That backflow undermines the effective removal of water, so the wet well level stays higher than intended. As soon as the control senses the level has risen enough, it starts the lag pump again, but because water is continuously slipping back, the pump reaches the shutoff level and stops, only to be quickly triggered again as rainfall continues. The result is rapid start‑stop cycling of the lag pump. The other possibilities would produce different symptoms. A check valve on the lag pump stuck closed would prevent discharge and either keep the pump from moving water or cause abnormal shutoffs, not rapid cycling driven by backflow. A stuck closed or clogged valve on the lead pump would alter how the lead handles inflow and change the lead’s cycling pattern, not specifically drive rapid lag cycling in a rainfall event.

Two-pump lift stations rely on check valves to keep discharges isolated when a pump isn’t running. In rainy conditions, the wet well level can swing quickly, so the lag pump should come on and off as needed without causing the water to flow back into the well.

If the lag pump’s discharge check valve is clogged, backflow from the discharge line can seep back into the wet well when the pump is supposed to be off. That backflow undermines the effective removal of water, so the wet well level stays higher than intended. As soon as the control senses the level has risen enough, it starts the lag pump again, but because water is continuously slipping back, the pump reaches the shutoff level and stops, only to be quickly triggered again as rainfall continues. The result is rapid start‑stop cycling of the lag pump.

The other possibilities would produce different symptoms. A check valve on the lag pump stuck closed would prevent discharge and either keep the pump from moving water or cause abnormal shutoffs, not rapid cycling driven by backflow. A stuck closed or clogged valve on the lead pump would alter how the lead handles inflow and change the lead’s cycling pattern, not specifically drive rapid lag cycling in a rainfall event.