Which device in a sewage lift station is used to sense the liquid level and trigger pumping?

• A. Float
• B. Gate Valve
• C. Vent
• D. Strainer

Answer: (A)

The concept being tested is how a sewage lift station knows when to start or stop pumping by sensing the liquid level. A float device, typically a float switch, does this job. As wastewater rises, the float rides up and activates a switch or sensor that sends a signal to the pump controller to turn the pump on. When the level falls to a set low point, the switch signals the pump to stop. This simple, reliable mechanism keeps the station from overfilling or running dry.

Other components in the options don’t perform level sensing: a gate valve changes flow in a pipe but doesn’t detect or respond to liquid level; a vent provides an airway for pressure equalization and does not measure level; a strainer removes solids from the flow and doesn’t sense or control pumping.