What does the Air Gap Do On a Dishwasher?

A dishwasher is a staple appliance in your kitchen. It makes our life easy in so many ways that you can’t even imagine, but it is very important to know about the parts and components that help dishwashers perform effectively and smoothly.

One such part that is not an original component of a dishwasher but helps it run smoothly is an air gap. Most homeowners are not aware of an air gap, what it does, and whether you need one with your dishwasher. In this article, we will discuss everything you need to know about a dishwasher air gap.

What is a Dishwasher Air Gap?

What is a Dishwasher Air Gap

A dishwasher air gap is a fitting that sits on the top of the countertop near your sink faucet. It rises about 2-3 inches from the counter surface and is one of the most effective methods to prevent drain water from going back to your dishwasher and flooding it. An air gap is a simple, easy-to-install and easy-to-maintain way of ensuring that your dishes don’t come out loaded with grime and dirty water.

Air gaps separate the hose running dirty water from the dishwasher and the drain carrying the dirty water from air gap to the garbage disposal system. Since these two pipes don’t cross each other, the risk of wastewater coming back to your dishwasher gets very low. However, clogs can develop over time in the air gap that can lead to drainage issues. This is why checking the air gap for blockages is an important part of dishwasher not draining troubleshooting.

Where to Install Dishwasher Air Gap?

Where to Install Dishwasher Air Gap

The best place to install a dishwasher air gap is the space between your kitchen faucet and the rim of your kitchen sink. If the garbage disposal becomes clogged and your sink floods with dirty water, the water will come out from the air gap and fall in the sink. In this way, you will not have to deal with a messy and dirty countertop.

How to Install a Dishwasher Air Gap?

Installing a dishwasher air gap is an easy thing to do if you have basic plumbing knowledge. Most homeowners can complete a DIY installation without the help of a plumber. The following steps will help you complete the installation process without any hiccups.

Locate the Air Gap Hole

Most kitchen counters have a predrilled air gap hole. Some have a rubber covering that you need to locate to reveal the hole. If your kitchen counter doesn’t have an opening, don’t worry, you can drill one yourself if you have the required tools with you.

You will need a power drill and a granite drill bit (1-3/8 inch). Ensure that you drill near the rim of the sink so that the air gap has enough space to drain in case of an overflow.

Connect the Hoses

Connect the Hoses

Once you are done with drilling, it is time to connect the hoses. Be careful while connecting the hoses. The drain hose of your dishwasher connects to the smaller leg of the air gap.

Now you will need to connect the air gap to the garbage disposal or your drain. For this, you will need a 7/8-inch tube. Measure and cut the required length and make the connection. Secure both pipes with clamps.

Set the Air Gap on the Counter

Remove the cover on the air gap and push it above the hole for the air gap. Tighten the air gap against the counter by tightening the nuts around its threads. Some models have one nut, while some have two for a more snug fit. Use a wrench to ensure that the air gap is securely fastened to the counter. Put back its cover.

Test Run

Once you install the air gap, run a full cycle on your dishwasher. Check for any leaks and ensure there are no water drops around the garbage disposal, dishwasher drain hose and the recently installed air gap.

If everything is good, you have just installed an air gap with your dishwasher.

How does a Dishwasher Air Gap Work?

How does a Dishwasher Air Gap Work

A dishwasher air gap has two branches that ensure that cross-contamination between dishwasher and drain. The physical air gap guarantees that it will never happen. The air enters the air gap from the opening in the cover and maintains a pressure that forces the drain water from the dishwasher back into the garbage disposal or your sink’s drainage system. When this opening is clogged from debris, the dishwasher faces drainage problems.

One branch connects the air gap and the dishwasher. The other branch goes down from the air gap to the garbage disposal. The dishwasher hose curves upwards to join the air gap. The dirty water comes into the air gap and is pushed into the other pipe by the air pressure at the top. Dirty water enters the second pipe and is carried toward the sink drain or independent drainage pipe for the dishwasher.

The two branches are beneath your sink, and the air gap head is above the sink. It is covered with a vanity cap usually made from chrome or stainless steel with openings that allow water to exit if the drain becomes clogged.

How to Clean an Air Gap?

How to Clean an Air Gap

Cleaning your air gap is an easy thing to do. Begin by removing the cap and removing any debris or dirt on it. Now use a sharp light to see if there is any blocking in it. Pour a jug of water into the air gap and listen to water draining in the sink. If the water is flowing freely, your air gap is clear of clogs and blocks.

Do I need a Dishwasher Air Gap?

While an air gap is not the only way to ensure smooth draining from your dishwasher, it is the most effective and proven method to reduce the chances of your dishwasher not draining properly. Moreover, it is easy to maintain and clean compared to other methods.

An air gap has no moving parts, so the likelihood of failure is very low. It uses a simple physics principle that work in many complex situations.

Many states require homeowners to install air gaps with their dishwashers. The reliability of an air gap is the reason why many plumbing codes across the US make it mandatory to install an air gap with a dishwasher.

We recommend that you don’t skip installing an air gap with your dishwasher. If you decide not to install, make sure you check the local codes before doing so.

Dishwasher Air Gap Alternatives

A couple of alternatives to the air gap can be used in places that don’t mandate an air gap. These options may not be as reliable as an air gap but do the needful. Let’s check them out.

High Loop

High Loop

A high loop is a common method of backflow that is often used in dishwashers and washing machines. It works on the simple principle of gravity.

In a high loop dishwasher, the drain hose from the dishwasher is raised to the highest point beneath the sink. The highest point of the loop is attached with a bracket. The hose is then connected to the garbage disposal or sink’s drain.

The dirty water from the dishwasher is forced up through the pipe by the drain pump in your machine. Once the water reaches the highest point in the loop, it falls to the other side of the pipe. The motion of falling water and gravitational pull stop the water from coming back to the dishwasher. However, blockages or debris in the drainpipe can sometimes block the flow of water.

Most manufacturers recommend raising the drain hose for at least 32 inches from the point where it leaves the dishwasher. If there is not enough space, you will have to install an air gap to prevent drainage issues.

Dishwasher Standpipe

Another method frequently used in place of an air gap is dishwasher standpipe. It is a length of a vertical pipe above a P-trap that water drains into. P-traps are commonly used to prevent sewage and odors coming back into your home and are commonly used in washrooms.

Standpipes are complicated structures and are less effective than air gaps and high loops. Most plumbers and manufacturers recommend not installing them with a dishwasher. If you are going with a standpipe, make sure that it is taller than your sink’s flood level, or water can overflow into your cabinet.

Final Words

A not-draining dishwasher is one of the most irritating problems you will ever experience with your dishwasher. But the good news is that the air gap will eliminate such problems.

All the best with your dishwasher!


  • Stephen Powers

    Appliance repair guy from Washington. I am majorly experienced in dishwashers, water filters and refrigerators, AMA on my twitter account.

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