What Is a High Loop Dishwasher and Why Should You Use It?

A missing high loop on dishwasher drain lines is one of the most common faults discovered during checkups. See Figure 1 below if you don’t know what your dishwasher drain looks like. Fortunately, this problem is generally an easy repair. Before we get to that, let’s discuss a high loop and why your dishwasher should have one?

High loop

What is a high loop? 

A high loop is when the dishwasher drain comes before its connection to your kitchen sink. There are two ways that it can be installed: 

  • One involves securing the hose near or atop a cabinet in some fashion.
  • Figure 2 below shows an example of how this might look if you’re going for maximum effectiveness under cabinets with low ceilings such as those found above ground level floors and kitchens without many vertical spaces available where plumbing fixtures like faucets could take up residence. Another option would have been installing close proximity discharge end into either type of p-trap (never onto them).

It is not suggested that the drain hose be cut at garbage disposal. When the disposer is switched on, it functions as a pump and can send dirty water back to your dishwasher.

High loop Diagram

What is the purpose of a high loop? 

A high loop prevents wastewater back-flowing from your sink to the dishwasher. If the drain hose is not elevated, there’s a potential for its run in the wrong direction and cause standing water at the bottom of the unit, which leads to mild cases of back siphoning due to increasing hydrostatic pressure needed to overcome the loop.

Do I need to install an air gap? 

Preventing back siphoning is easy with an air gap! By introducing some additional work, municipalities require these to prevent negative pressure from entering your dishwasher and causing flooding. The drain hose connects underneath the sink near where you’ll be putting down a countertop or installing another piece of plumbing. This will create an empty space for water flow to travel without any resistance through this new section outside its normal boundaries – which could cause nasty suds-ups if not done correctly!

In my experience, most sinks today function correctly with only a high loop installed, but if you’re having trouble with back siphoning, you might want to have an air gap put in.

Dishwasher Air Gap

How do I install a high loop?

There are many ways to do it, but the easiest is with a screw and a zip tie. The total install time should be under 5 minutes. Here is a video I found of a simple high loop installation.

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