The HSD series are submersible single-phase portable pumps. The shaft-mounted agitator prevents "Air Lock" that tends to take place on vortex or semi-vortex pumps*. The rubber/resin-made stand protects the floor surface from scratching.
The benefit of a vortex impeller over a channel impeller is the minimized risk of clogging. The vortex impeller creates a revolving mass of water which forms a whirlpool. A whirlpool is a funnel shaped opening is created downward from the water surface. It can be developed by water flowing out of a small opening in the bottom of a basin, a reservoir or by a pump. Impellers creating this Vortex are called vortex impellers. A Vortex impeller is also a better choice when the pumped liquid has a high content of sand. The efficiency of a pump with a vortex impeller is typically lower than a pump with a channel impeller.