A float sensor, sometimes called a float switch,  is a device that is used to sense the level of a fluid. It acts as a mechanical switch. There is a float ring surrounding the sensor. When the float is at the bottom, the switch is open. When water level rises, it pushes the float upwards and the switch closes.    Our float switches come with an o-ring to indicate how far the float ring needs to rise until the switch is closed.  When testing your MySpool Water Level Alert, you can think of the float sensor as a push button switch.  When the float ring is at the o-ring level or higher, the switch is depressed.  Letting the float ring down is equivalent to letting go of the switch.  This is how a HIGH-WATER LEVEL Alert works.

To change to a LOW-WATER-LEVEL Alert you need to flip the float ring. This video shows how to to that.