In a lift station, if the lead pump check valve is lifting arm up, what is the most likely cause of the issue?

When the lead pump check valve is lifting its arm, it indicates that there is a problem with the flow of water or waste from that pump. The most likely cause in this scenario is a clog in the follow pump. When a follow pump is clogged, it can create backpressure against the lead pump. This backpressure can prevent the lead pump from operating properly, leading to an uncommonly high rise in the arm of the check valve.

In a properly functioning lift station, the lead pump operates to move wastewater through the system. If there is a clog in the follow pump, it can interfere with the flow and create pressure conditions that are reflected at the check valve of the lead pump.

Understanding how the pumps work in relation to each other is crucial in diagnosing issues. The lead pump is meant to handle the primary load while the follow pump acts as a secondary backup, kicking in when needed. If the secondary pump is not able to perform due to a clog, it can disrupt the entire system and cause the check valve in the lead pump to react abnormally.