the dishwasher drain path is from the dishwasher to an air gap above the top of the dishwasher, then down and into the disposal drain nipple or a tailpiece fitting for the dishwasher outlet. that inverted cap in the dishwasher is a high water cutout switch. when you take out the bottom tray, you remove a nut which frees up the tower. beneath this is a plastic or nylon chopper. on the pump shaft is a macerator blade . way down at the bottom is the pump impeller.