Set your floats to your water level in the sump or tank depending on your setup. plug in the pump to the black outlet and plug your floats into the computer plug above the outlet when your water level falls the lower float will turn the outlet on to pump water into your tank. now if the float sticks on, the second float will cut it off. so its redundant or protected from overflowing too much water. i use this with kalk water to supplement my tanks alk, cal, and mag.