How to Install Dishwasher Air Gap Under Countertop

Your plumber just finished installing your dishwasher, and they are advising you to consider an air gap. The problem is, you don’t know what it is and how to install it.

Well, don’t worry; we’ve got you covered.

How to Install Dishwashers Airgap Under Countertop

First, understand that you need an air gap to protect your dishwasher. Flooding from wastewater can be a real pain in the neck.

This is why most plumbing jobs come with an air gap as a mandatory requirement. But how do you install an air gap?

Read this guide to find out.

Understanding Dishwasher Air Gap Under Countertops

Before discussing the steps, we must first understand what a dishwasher air gap is. This will paint a picture of its usefulness and why you need it.

It would be best if you had several things under your countertops. One of them is ensuring proper drainage and airflow.

Flooding water is one of the major causes of issues under the sink. It can lead to rusting of metal and the destruction of wood.

A dishwasher air gap is equipment above the sink and countertop that prevents dirty water from returning to the dishwasher. In other words, it’s like a valve that prevents the backflow of contaminated water.

This is one of the best ways of ensuring wastewater does not make its way back into clean water. It’s an assurance that all the water in your house is safe.

Imagine doing your dishes through a wash cycle, and then you notice some dirt from the garbage disposal streaked to it.

An air gap seeks to keep such things from happening. It clearly separates the pipe from dirty water and the one from the main drain.

The lack of intersection between these two hoses means you never have to worry about dealing with wastewater again after disposal.

Installing Dishwasher Air Gap Under Countertops – The Guide

Most people will want to turn to a plumber or an expert to do any installations in their kitchens.

However, some stuff you can learn to DIY and save some cash. Installing a dishwasher air gap under a countertop is one of them.


Before we look at the guide, there are several things you need to keep in mind. They include the following.

Properly assembling the air gap

A dishwasher air gap might sound easy to install. But that is not entirely true since it takes some understanding to get the job right.

For instance, any wrong step when assembling the air gap might mean starting all over again.

You need two hoses under the countertop piping and a cap for decoration. The air gaps are made from flexible rubber and will probably look like a “Y” once installed.

Carefully follow the manufacturer’s instructions, ensuring everything is done accordingly. Note that this is a crucial step that will majorly affect the performance of your installation.

The location

Another important consideration is the exact location of the air gap. Remember to pry protective holes under the countertop and then make enough room for the installation.

Consider watching some of the many online videos that teach you how to install such an item. It will save you some time and money you would otherwise spend on damaged countertops.

Connecting to the drainpipe

A dishwasher air gap seeks to prevent water damage and the mixing of waste with clean water. You might end up doing more destruction than good if you are not careful with the current plumbing.

The drain hoses from the air gap will connect to the dishwasher, while the other end will connect to the drain line. A good connection is required to ensure proper functioning.

Connecting the air gap to the garbage disposal

Every garbage disposal unit comes with accommodation for air gap drain pipes. Once connected to the sink under your countertop, you now need a proper connection to the garbage disposal.

A mechanical clamp fitting is used here.

Installing your dishwasher air gap – steps

Now that you know where to start, we can get into the steps of installing one. Read these steps carefully because you will need a well-finished drainage system.


  • A dishwasher air gap
  • A hacksaw
  • Screwdriver
  • A hammer
  • A hose
Installing your dishwasher air gap

Step 1: Prepare your workspace

Never start working without knowing what goes where. Preparation is always key to delivering a great job.

The first step is to understand how an air gap works. We have discussed this above already – it should not be an issue.

After that, follow these preparation steps:

  • Pull aside parts of the air gap. These include the decorative gap, top cover, top retaining nut, counter gasket, and more. Keep the bottom retainer on the gap intact.
  • Set the bottom to retain the nut to meet the sink thickness.

With the air gap separated, you are ready to start the installation.

Step 2: Start the installation

  • Start by fixing the air gap through the hole under your sink. It needs to go through the sink properly.
  • Insert the counter gasket into the gap stem on the countertop. This is among the most crucial parts, so you must install it carefully.
  • Screw the top retainer nut to the air gap step. You should see this part clearly above the counter gasket.
  • Once it’s well screwed, use your hands to tighten the bottom retainer nut until it is holding firmly. Check again to make sure it fits right into space.
  • Move to the 5/8-inch inlet drain pipe and connect it firmly to the dishwasher pumping line. Check again to ensure your pipe is secure. The last thing you want is to deal with leakages from loose connections.
  • The next step is to connect the 7/8-inch outlet drain hose to the correct line. You have the choice of connecting it to the garbage disposal or to the waste line.

Suppose you are not sure which connection goes where. Try watching online videos that open up these air gaps. It will present a clear view of what is expected.

Step 3: Finish up the installation

You are not yet done. The last and crucial step too is to properly finish the installation.

  • After installing the dishwasher air gap under the countertop, secure each end of the hose using hose clamps. This will keep the hoses from sliding off and water from leaking out.
  • Screw back the top cover nut using a screwdriver. Press the decorative cover on the appliance until it fits perfectly.
  • Try it out. You need to make sure the dishwasher air gap is working properly. Check for any leakages in the pipes and anything else that might seem out of order.

You have now successfully installed a dishwasher air gap. Don’t forget to try it out and ensure it works perfectly before closing your work area.


Some of us have faced a situation where we have to deal with a clogged kitchen sink. It causes dirty water to flow back into the dishwasher, contaminating the inside.

Installing an air gap is the best way to ensure such issues never arise.

You don’t even need to look for an expert or pay huge amounts of money to get the job done. A single afternoon is enough, and your kitchen sink drainage is secure.

We hope this guide has been helpful. But if you are unsure what to do, consider hiring a professional plumber.

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I am a professional appliance repair expert and write articles that help average users diagnose and troubleshoot their kitchen gadgets, like microwaves, dishwashers, etc. I’m a foodie by heart and love reviewing food recipes, ingredients, and the cookware products used in them for meal preparation.