Randy Holmes-Farley
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My Tank Thread
A water loops that keeps the impeller cavity flushed and cooled. In the early generation of wet magnetic drive pumps, the heat in the impeller cavity and overall lack of water movement would cause rather quick calcium precipitation deposits on the rotor (impeller magnet) and back end of the cavity and bearing.
Some pumps do a much better job at this than others. Look at the pump photo above, There is an intake port at the top that is connected to the hole at the rear of the impeller. The impeller has a hole through the shaft. This keeps water moving around and through the impeller, driven by the pressure difference between the water in the center and edge of the volute.
Ok, thanks. I simplistically assumed a high flow pump would have little time for the water to heat up, and the heat on the impeller wouldn’t be reduced by much by even more flow.