Dishwasher High Loop and Why You Need One

In my experience, a missing dishwasher high loop is one of the most common defects noted in a home inspection report. If you’re unsure what your dishwasher drain looks like see the picture below. Fortunately, this is an issue that can be resolved easily by homeowners, but before we get started, we should learn what dishwasher high loop is and why dishwashers should have one.

What is a Dishwasher High Loop?

A high loop is when the dishwasher drain is elevated right before it’s connection to the kitchen sink’s drain. It’s important to remember the following about your connection from the dishwasher drain pipe to your plumbing:

• The high loop should be installed as close as possible to the underside of the cabinet for maximum effectiveness.

• The connection should be before (upstream of) the P-trap on your sinks plumbing.

• A connection should never be at the P-trap or after (downstream of) the trap this leads to backflow and sewer gases coming from the drain lines.

• Avoid connections to garbage disposals.  Disposers could potentially send dirty water back into your dishwasher when they are turned on.

What Is the Purpose of a High Loop?

If you notice standing water at the bottom of your dishwasher between washing cycles, chances are the drain hose is not elevated enough. There are two reasons why dishwashers must have a high loop. First, it’s paramount to ensure that wastewater drains properly during the drain cycle and to prevent siphoning. The second reason is to prevent contaminated water from back flowing into the dishwasher from the garbage disposal or sink drain.

Pro Tip: While there are new dishwashers that have a high loop built in, the installation instructions from various manufacturers all say to install the high loop underneath the sink. 

Do I Need To Install an Air Gap?

Installing an air gap in a drain line is the only surefire way to prevent back siphoning. However, it requires a bit more work and will be more expensive. Often these devices range from $10 to $45 and will require cutting into your countertop. Air gap devices are used to form siphon breaks in the same way as the high loops. Many municipalities find high loops to be acceptable on their own, but some require air gaps. The majority of sinks work perfectly fine with just a high loop installed nowadays. However, if you experience back siphoning, you may wish to contact a licensed plumber about having an air gap installed.

How Much Does It Cost To Install an Air Gap?

An air gap device for dishwashers can be bought for $10-$30 and installed by a qualified plumber, appliance installation service, or a handy homeowner. It’s important to remember that when purchasing installation services that each contractor’s pricing will vary. It’s best to compare installation costs from various service providers. Often you can negotiate that the air gap be included with the purchase and delivery of a new dishwasher from your retailer if they provide installation services. Installing an air gap should take no more than an hour unless your drain pipes need to be rearranged.

How Do I Install a High Loop?

There are many methods of installing a high loop, but the easiest is using a screw and zip tie. Often new dishwashers will include a clip for the drain line in their packaging. It’s often just a matter of finding a good spot to connect the drain line. Five minutes should be enough to install a high loop and voila, you’re done. Here is a simple installation video provided by GE Appliances that is 3 minutes long and shows how to install a high loop.

How Much Does It Cost To Install a High Loop?

As seen in the above video, It can be installed for free. The real cost for this type of install is 5 minutes of your time and less than $2 for the screw and a clip or zip tie.

Home Inspection Services in Orlando, FL

Do you have any questions about high loops or air gaps? Your home inspector is always an excellent resource for information about your home. At HOMESHAPE Inspections our homeowner resources are always being updated to help homeowners well beyond their home inspection. If you have a question about your home don’t hesitate to Contact Us. HOMESHAPE Inspections can answer your questions when we come out for a home inspection in Seminole, Orange, and Volusia Counties, FL.