The circulation pump is your dishwasher's motor. It sucks up the water that has entered the tub in order to send it to the spray arms. The water goes through several filters and returns to the pump for a new cycle.The circulation pump is your dishwasher's motor. It sucks up the water that has entered the tub in order to send it to the spray arms. The water goes through several filters and returns to the pump for a new cycle.