There is an impeller inside the micro bilge pump, which rotates at a high speed after being energized, rapidly throwing out the water near the impeller, thus forming a vacuum (negative pressure) near the impeller. The pressure difference between the external atmospheric pressure and this real space pushes water near the submersible pump into the pump and out through the inlet (often the many mesh holes at the bottom of the pump). At the same time, the external water is sucked in, with the "floating switch", can be in the bottom of the water to the warning water level height automatically start the micro submersible pump drainage, water level drops to the warning low automatically cut off the power to stop the micro submersible pump, avoid dry burning.