Sump pumps are activated automatically when the water level in the sump pit reaches a certain height. The homeowner can set the pump to activate at any depth he desires by adjusting the float mechanism of the sump pump.
How Sump Pumps Work
Seeping water or water runoff is gathered in the sum pit. As the water collects, a float will rise with the water level. The float controls an on/off switch for the pump. When the float rises to a preset height, the pump will be switched on. The pump will continue to operate until the float drops low enough to disengage the switch. The pump is then idle until the water level rises again.
Sump Pump Float Mechanism
Different types of sump pumps use different types of floats. A pedestal pump will generally have a bulb-style float attached to a metal rod which activates the motor's switch. Other pumps use floats that are on arms which will raise and lower with the water level. A tethered float is one that is attached to the pump using a tethering device.
Tethering Sump Pump
As the water level rises, the float rises as well. The tether is slowly released as the float rises. The tether will be set to activate the pump when a certain amount of tether has been released. As the water levels drop, the tether becomes slack and the float descends back to the starting position.