The HSZ-series is a submersible single-phase autmatic portable drainage pump. The automatic operation, controlled by a single float switch, reduces cnsumption and extends operating life. Though the pump is a single-phase unit, it has the durability equivalent to three-phase drainage pumps, since te wear parts are made of abrasion-resistant materials. The side discharg, spiral design allows smoother passage of the sucked solid matters. The shaft-mounted agitator prevents “Air Lock” that tends to take plae on vortex or semi-vortex pumps.