The magnetic impeller is what makes the water pump work, and is commonly the reason for a decrease in flow rate, due to lack of cleaning and maintenance. Clean the impeller and the impeller well of the pump regularly to avoid problems, and prolong the life of your impeller and pump. The impeller is easy to access; the impeller cover needs to be removed by removing the screws holding it in place. Gently grasp the fan blades and pull the impeller gently out of the impeller well for maintenance.