What is a Dishwasher Air Gap?

Dishwashers can save you a lot of time in the kitchen. Not only that but they also use less water and are more efficient compared to washing your dishes by hand.

Like most appliances, these machines consist of several parts, all of which work together to clean your dishes. These include the spray arms, water inlet valve, dispenser, filter, and heating element.

There’s also the dishwasher air gap, which is necessary for proper performance.

What is it? What does it do? Do all dishwashers come with one? Keep reading for all the answers.

What is the Dishwasher Air Gap?

The dishwasher air gap is a small, anti-backflow device that’s designed to prevent dirty water from flowing back into the dishwasher.

If there’s a blockage in the sewage line, the water will drain into the sink through the air gap, instead of the dishwasher. That way, your dishes will remain clean.

How Does a Dishwasher Air Gap Work?

The dishwasher air gap works by separating two branches of hose with a gap of unpressurized air. One of the branches is attached to the garbage disposal while the other is connected to the dishwasher itself.

When you run the dishwasher, the wastewater is pumped into the air gap through one of the hoses and is released through the second hose to the drainage site. In other words, the dishwasher drains directly to the waste line.

Assuming that it’s installed properly, no air or water should be expelled from the gap.

Why Do We Need a Dishwasher Air Gap?

The air gap leads dirty water away from the dishwasher so that it can clean your dishes properly. More specifically, it will push the wastewater into the garbage disposal through the drain hose.

Without an air gap, wastewater from the kitchen sink drain can backflow into the dishwasher and contaminate your dishes.

Do All Dishwashers Have Air Gaps?

Most states have plumbing codes that necessitate the use of air gaps in commercial and residential sinks. For example, California, Hawaii, and Washington, all list air gap installation as a mandatory plumbing procedure.

If you do not install an air gap, your house will not be up to code, meaning you will have to pay more for your homeowners insurance.

Where is the Dishwasher Air Gap Located?

Most dishwasher air gaps are covered by a stainless steel or chrome cylinder and can be found at the back of the sink, parallel to the faucet.

If you were to look underneath the countertop, you would see that the air gap fitting connects to two branches of hose, one that’s attached to the dishwasher and another that connects to the garbage disposal.

The slats of the air gap should also be pointing toward the sink – that will allow the water to flow into the sink as opposed to behind it.

How Much Does Dishwasher Air Gap Installation Cost?

Air gap devices are relatively cheap and can be bought for $10 to $30 at home improvement stores. Professional installation by a qualified plumber, however, can cost anywhere from $100 to $150, depending on how much they charge for labor.

Common Dishwasher Air Gap Issues

Various things can cause the air gap to malfunction and if that happens, water can flow out. Here are some of the most common situations:

The Dishwasher Air Gap Isn’t Installed Properly

The air gap system requires different sizes of drain hoses, which you can check by looking underneath the sink. If the ‘out’ hose (the one attached to the garbage disposal) is smaller than the ‘in’ hose, it won’t be able to function properly.

Similarly, if the knockout plug wasn’t removed during installation, water wouldn’t be able to flow into the ‘out’ hose. In that case, you’ll need to disconnect the hose connected to the disposal to allow the water to flow out before removing the plug, which is recessed into the inlet.

You Have a Clogged Air Gap

Food particles and grease can clog the air gaps over time and that can cause water from the dishwasher to back up and spill into the sink.

To remove the clog, you’ll want to first remove the air gap cover. Once it’s off, place a paper towel tube over the openings and blow into the space – that will help dislodge any particles or debris that are stuck.

Alternatively, you can use a long-handled bottle brush. If that doesn’t work, the blockage may lie beyond the drain lines, in which case you will need to remove the p-trap to remove the clog.

Understanding Dishwasher Air Gaps – FAQs

Can you use a dishwasher without an air gap?

While some dishwashers don’t require an air gap to operate, it’s highly recommended that you use one as it will prevent contaminated water from flooding into the dishwasher. Many states also have plumbing codes that require built-in air gaps.

How does the air gap work?

The air gap separates two branches of drain hoses with an unpressurized gap, which helps prevent dirty water from re-entering the dishwasher and contaminating your dishes.

Where is the dishwasher air gap located?

The cylinder fitting can be found at the back of the sink. If you look under the countertop, you’ll see a drain hose leading to the dishwasher and another that is connected to the disposal unit.