What is a high loop?
A high loop relates to the way that your dishwasher drain line is connected through the cabinetry to your disposal or plumbing under your sink.
Rather than having your drain line run along the bottom of the cabinet and up into your disposal, a properly installed high loop is installed in such a way that as the drain line leaves your disposal, it goes up and is securely attached to a high point in your cabinet as it runs to the dishwasher.
This can be done using clamps or straps or some other fastening device that securely attaches the drain line to the cabinet wall or countertop without crushing the line itself.
Why is a high loop important?
The high loop is critical in the process of installing your dishwasher. If the high loop is not installed, food and water from your sink and disposal can collect at the low point of the drain line. This can cause foul water or decaying food to back up into your dishwasher causing odors or malfunction.
How should a high loop be installed?
Installers often use a bracket attached to an upper portion of the cabinet or the bottom of the countertop to permanently hold the drain line in that elevated position. Alternatively, some use zip ties.
This picture illustrates what you will see under your sink if a high loop is installed. You’ll see the dishwasher drain line exiting the disposal and then going up to the top of your cabinet as it makes its way to your dishwasher.
This may seem like a small detail but it can cause problems for you if its not done correctly.