Centrifugal pumps, whether submersible or not, are designed for the most part to operate in one direction only.
When liquid enters the center or eye of the impeller it is subjected to centrifugal force that moves the liquid towards the discharge port on the pump.
The path for liquid to flow is determined by the shape of the impeller and the design of the pump body or volute.
If the impeller is run in reverse direction the liquid may still be discharged from the pump due to centrifugal forces overcoming the normal flow path.
This is very inefficient and can cause serious problems including cavitation, loss of performance, bearing and seal issues.
If the impeller is on a threaded shaft it may unscrew the impeller.
It is always good practice to check impeller rotation before you start pumping.
Most (but not all) Hydra-Tech Pumps rotate in a counter-clockwise rotation (looking at the impeller inlet from the bottom).
We mark the Pressure and Return ports when the pumps are shipped.
This assures proper rotation when properly connected to a hydraulic power source.
Click on this link to see how to properly connect our pumps to your hydraulic power source:
Hydraulic Schematic Customer Supplied
Click on this link to see a pump impeller rotating properly: