What Is a Dishwasher Air Gap — and What Does It Do?

Your dishwasher makes those dirty dishes sparkling clean without hours of scrubbing, so you might not think much about how it works as long as it keeps working.

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But sometimes it's helpful to have a better understanding of different appliances and how they operate. One optional component your dishwasher might have is an air gap. Find out what a dishwasher air gap is and what it does.

What Is a Dishwasher Air Gap?

A dishwasher air gap is a small device that sits near your sink above the counter. It typically has a chrome cylinder cover over it. As part of the dishwasher's draining system, the air gap prevents the backflow of dirty water into your dishwasher.

What Is the Purpose of an Air Gap?

When the wash cycle ends, the dirty water drains from the dishwasher and through your kitchen plumbing. The dishwasher air gap prevents that dirty water from flowing back into the dishwasher so your clean dishes don't get contaminated.

The dishwasher air gap works by creating a space between two hoses. One hose connects the dishwasher to the air gap. The dirty water travels into that hose and through the air gap. From there, it travels into the second hose, which connects the air gap to the kitchen plumbing. Because the air gap is unpressurized, the water can't flow backward through it.

Does a Dishwasher Need an Air Gap?

Technically, you can install a dishwasher without an air gap. Many new dishwashers offer installation instructions both with and without an air gap. However, your appliance needs a dishwasher air gap or some type of device to prevent the dirty water from flowing back. It's important for getting your dishes clean and avoiding contamination from the dirty water.

Some states require dishwasher air gaps, so you might be required to add one if you install a new dishwasher. Your local building codes might also specify you need an air gap for your dishwasher. Review the local codes related to plumbing to determine if you need this plumbing device.

Whether or not it's required in your local building codes, you might decide it's worth the investment for your family. It helps keep your dishes and kitchen sanitary.

Alternatives to Dishwasher Air Gaps

Some people don't like the look of the dishwasher air gap sticking up above the sink. Others don't want to make an extra hole in the sink or countertop. There are alternatives to dishwasher air gaps.

High Loop

A high loop is typically considered the best alternative to an air gap. It generally offers reliable backflow prevention. In this method, the dishwasher drain line attaches to the bottom of the counter using a bracket before draining down into the plumbing. This forces the water to run up before going down at a sharp angle, which makes it unlikely to move backward into the dishwasher.

Standpipe

While not as effective or efficient, a standpipe is another alternative to an air gap. It uses a pipe that's at least 2 inches in diameter, and it's installed vertically above the P-trap under the sink. This option is usually more complicated and less reliable than an air gap.

Some newer dishwasher models have air gaps or backflow prevention devices built into them. The devices only allow the water to flow one way out of the appliance. Keep in mind that these built-in devices typically don't satisfy building codes that require dishwasher air gaps.

When it comes to reliability, a dishwasher air gap is usually your best bet. It requires an investment to install it, but you have peace of mind knowing the backflow prevention is effective.

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Dishwasher Air Gap Maintenance

You shouldn't need to do anything to your dishwasher air gap once it's installed. However, it's possible for the air gap to become blocked with food particles if you don't rinse your dishes well before placing them in the dishwasher. If you notice water coming out of the air gap, you might be dealing with a blockage.

When this happens, simply remove the cover and clear the debris from the air gap. A bottle brush works well for cleaning out the device. You may want to clean the air gap occasionally even if it's not clogged to keep things flowing well.