Changing oil in small pumps can be challenging due to the design of the pump housing. There is a cavity in the bottom of the housing that traps water and contaminants. We have started using a small handheld vacuum pump to completely remove the water and/or old oil from this cavity resulting in much cleaner oil with each change-out.
We get 10 additional ounces or more out of the pump using this method versus only opening the drain plug.
