NOCTI Plumbing Practice Test

A float switch is the sensing device that starts and stops a sewage ejector or effluent pump. It’s a buoyant mechanism placed in the pump basin that rises with the wastewater level. When the liquid reaches a preset height, the float switch closes the electrical circuit and powers the pump on. As the pump reduces the level, the float falls, opening the circuit and turning the pump off at a lower threshold. This level-based control is essential for automatic, reliable operation in a wet well or sump. Other devices aren’t the primary initiators here. A thermostat watches temperature, not liquid level. A pressure gauge measures system pressure and doesn’t directly start the pump. A switch relay can control the power circuit, but it’s driven by the float switch (or a control panel) rather than serving as the sensing element that triggers starting the pump.