What Is a Dishwasher Air Gap?

Have you ever wondered what that small cylinder is on your kitchen sink? That little bit is your dishwasher's air gap. To the naked eye, it doesn't seem like much. But when it comes to plumbing and the cleanliness of your dishwasher, the air gap is an essential, and sometimes legally required, part of the system. 

So, what is a dishwasher air gap, and do you need one?

What Is a Dishwasher Air Gap? 

A dishwasher air gap is a small cylindrical fitting that connects the kitchen sink to the dishwasher. It sits elevated on the sink above the dishwasher to prevent dirty dishwater from flowing back into the appliance and all over clean dishes during a cycle. It ensures your dishes stay clean, and the wastewater funnels into the kitchen sink plumbing. 

How Does a Dishwasher Air Gap Work? 

The dishwasher air gap works using simple physics. The elevated air gap creates two channels in the hose: the dishwasher to the air gap and the air gap to the disposal or sink. When a dishwasher drains, it pumps the dirty water through the tube, reaching the peak, then falling down the other side and draining out. 

The cylinder above the sink has a literal gap with a notched hole. This air gap prevents contaminated water from flowing backward. If the air gap is clogged, the contaminated water will simply flow into the sink, not back into the dishwasher. 

Where Is the Dishwasher Air Gap?

The dishwasher air gap is installed on the kitchen sink, most often next to the faucet handles. It’s cylindrical in shape and often chrome or stainless steel. You may have seen dishwasher air gaps before and not even noticed them.

Is My Dishwasher Air Gap Working?

If water starts to come out of your dishwasher's air gap during a cycle, it’s an indication that something is wrong. Water from your dishwasher's air gap is likely a sign of a clog in the tubing. If you can’t clear the gap on your own, it’s time to reach out to a professional who fixes dishwashers. Contact a dishwasher repair service near you to clear the line of clogs and bring your air gap back into shape. Having a pro replace a dishwasher air gap costs between $80 and $150. But, if your dishwasher isn’t cleaning, it could indicate additional issues. 

Do I Need a Dishwasher Air Gap?

Some, but not all, states require dishwashers to have an air gap to be up to code. If you live in one of these states and install a dishwasher without an air gap, it could cause issues if you try to sell the home or repair the washer. Plus, you could be sending dirty water back into a clean dishwasher.  

Even if your state doesn’t require a dishwasher air gap, you’ll need it, or an alternative, to prevent wastewater from flowing back into your dishwasher. A plumber may recommend a high loop or a standpipe instead, but neither is as effective as an air gap at preventing backflow. 

Additionally, some dishwashers come with built-in air gaps, but many of these built-in air gaps don’t satisfy state plumbing codes. When installing a new dishwasher, it’s best to consult with an experienced plumber for best practices.