Dishwasher Air Gaps

What are they?   What do they Do?

Have you ever run a load of dishes in your dishwasher, only to find dirty dishes or brown, murky water in the tub after the load is done? You’re perplexed. After all, it’s your dishwasher’s job to clean the dishes, not leave you with a mess to clean up.

Unfortunately, this problem isn’t all that uncommon. Sometimes clogged drains or sinks can send dirty water back into your dishwasher via backflow due to a stoppage further down the drain line.

That’s where air gaps come in. But what exactly are air gaps? How do they work? Do you need one? We answer all these questions below.

What is a dishwasher air gap?

Air gaps are fittings that are attached to your counter or directly on your sink with a small outlet located a couple of inches above your kitchen sink. In short, air gaps separate the hose running wastewater from your dishwasher from the hose running to the drain. As a result, these two pipes never intersect so there’s no chance of dirty water contaminating your dishwasher, or its contents.

Depending on where you live, municipal plumbing code might dictate that you have to install air gap along with your dishwasher. Whether or not that’s the case, air gaps are the safest, most efficient way to guarantee backflow never gets insider your dishwasher.

How does a dishwasher air gap work?

Dishwasher air gaps are exactly what they sound like, fixtures that create a gap of air. One segment of the dishwasher air gap connects to the dishwasher. The other branch runs from the air gap into your garbage disposal.

As wastewater leaves the dishwasher, it goes into a hose that runs upward to the air gap. At this point, the water pours down through the air gap and into the second tube. From here, it continues its way downward to either a garbage disposer or directly into the drainage location.

Both branches of the dishwasher air gap are beneath your countertop. The heading will be visible above the counter’s surface near your faucet or soap dispenser. Under the heading is the actual air gap. This section of the fixture has holes that will release water into your sink if the tubing or drain become clogged. If you notice water exiting your dishwasher air gap and flowing into the sink, there’s a good chance your drainage tube or drain pipe has a blockage that needs to be cleared.

Do you need a dishwasher air gap?

The short answer is yes, if you want to keep your dishes clean, and your dishwasher from becoming contaminated.

Even though there are a number of other methods out there to keep your dishwasher from becoming contaminated, air gaps are the only one proven to do the job under any circumstance. The reason is that they don’t have any moving mechanical parts. They rely solely on basic physics and gravity to do their job.

If you have a garbage disposer and a dishwasher, you will definitely want to use an air gap. If you didn't use an air gap and connected the dishwasher discharge hose directly to the garbage disposer you can be sure eventually you will experience contaminated water in your dishwasher. Looping the drain hose and attaching it to the bottom of the countertop near the sink will not help. When a disposer is working it is pushing (pumping) water to the drain. If there is a stoppage in the drain, and an air gap is not installed, the disposer will pump the waste back into the dishwasher (loop or no loop). This is not a scenario you want to experience.

Think about the health benefits of having a contaminant-free dishwasher. Dirty dishes and water used to clean them aren’t exactly appetizing to think about. Between the food scraps, water and warm temperature, a dirty dishwasher is hotbed for bacteria. Dishwasher air gaps alleviate all those worries.

How do you install a dishwasher air gap?

Installing a dishwasher air gap is something you can do on your own.

Some parts and tools you may need:

Pro Tip: Before purchasing any parts, check and see if your dishwasher includes any of the items listed above. Many new dishwashers include hoses and parts to help you install it.

Start by locating a place the air gap can be mounted on your sink. If it’s not readily visible, it’s probably covered by a small disc known as a faucet hole cover. In the event you can’t find a pre-drilled hole, you might have to drill one yourself. It's not recommended you drill a hole in your sink unless you have a stainless steel sink. You may be able to change your faucet on your existing sink to cover up less holes and open up a hole for the air gap. The air gap must be able to drain water into the sink should there be a drainage problem.

Next, you need to connect the dishwasher drain hose to the air gap. The drain hose should be 5/8” and fit with the 5/8” leg (smaller of the two legs) of the air gap. Stainless steel hose clamps should be used to connect the hose to the dishwasher and to the air gap.

Now that the dishwasher drain line is installed on the air gap, push the air gap up through the hole in your counter. Secure the air gap by threading the nut along the air gap’s threads. Once you’ve tightened it by hand, use a wrench and tighten it a quarter of a turn more to finish the job. Overtightening can damage the air gap threads.

You are now ready to install the 7/8" drain hose from the air gap to the garbage disposal. You want the 7/8" hose to fit smoothly from the air gap to the disposer without kinking the hose or letting it sag. Either one of these conditions can cause the discharge water to back up at that point and push out through the air gap and into the sink. This is why the 7/8" hose should not be installed before mounting the air gap to the sink. Use stainless steel hose clamps to secure both ends of the hose.

After your air gap is installed it's a good idea to run your dishwasher through a complete cycle to make sure there aren't any leaks.

Final Thoughts

There’s a lot to consider when it comes to making sure your household plumbing functions as it should and keeps your water supply clean. Fortunately, dishwasher air gaps virtually guarantee your dishwasher will remain free of waste water and contaminants. What’s more, they won’t set you back much money and are easy to install.



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