Dishwasher Drain Line High Loop

The purpose of a dishwasher high drain loop is to prevent back flow of water.

Dishwasher drain line high loop.

In the high loop method the drain line of the dishwasher is looped up as high as possible under the countertop before it runs back down to connect to the drain system. In some areas this high loop method is an allowable option but make sure to check. Figure 2 below shows the basic configuration of an installed high drain loop under a kitchen sink. The high loop does not prevent siphoning.

The water can flow back into the dishwasher which will leave water in the bottom of the dishwasher. But now it seems that most modern dishwashers now come with a loop of this type pre installed on the side of the unit. It provides a pressure break in the drain line that prevents the possibility of dirty drain water being back siphoned into a dishwasher filled with clean dishes thereby contaminating them. A high loop in the drain line of a dishwasher is one method of preventing backflow of fluid to the dishwasher.

What is a high loop. In the photo above right the dishwasher drain line was properly installed with a high loop and securely fastened to the underside of the countertop which also allows for the proper slope of the drain to the disposal. The high drain loop is also there to prevent improper drainage of water while the dishwasher is running. In the past i think this had to be created manually when the drain line was installed under the sink.

Dirty water entering the dishwasher and not draining could be because there is no air gap or high drain loop installation. A high loop should always be installed with the dishwasher drain line to prevent backflow of waste water to the dishwasher. The high loop should be fastened secured to the bottom of the countertop. Drain line configured in a high loop directly to drain an air gap fitting is a safety device mounted on your sink or countertop through which the dishwasher hose passes on its way to the drain.