A dishwasher drain line may be installed directly onto the garbage disposal. All garbage disposals come with this attachment. If installing a new garbage disposal and are using the provided connection to drain your dishwasher, be sure to knock out the plug. See manufacturer’s details for further instructions on the proper method of knocking out the plug.
The other method is to connect the dishwasher hose directly to the drainage piping under the sink. The dishwasher drain line needs to be connected between the sink and the p-trap. The dishwasher drain line needs to be looped up (curved) towards the top of the cabinets. This upward loop keeps water from draining back into the dishwasher.
The picture here shows the dishwasher drain line. The line drains from right to left and is connected to the garbage disposal which is out of sight in this picture. Notice that the dishwasher drains line is coming from the top of the cabinets creating an upward loop. For proper installation of dishwasher drain line call your local residential plumbing company, Mock Plumbing.