What Is The Thing Next To The Kitchen Faucet?

Next to your faucet, there’s a small, cylindrical metal tube. It doesn’t have any apparent use, nor does it make noise, spurt water, or anything of the sort.

So, what is it? What does it do?

Does it even have a purpose?

That random little metal tube is an air gap for your dishwasher. It serves a crucial purpose in keeping your dishwasher functional and preventing it from washing your dishes with dirty water.

This article explores the ins and outs of that seemingly random addition, so continue reading to learn more!

Dishwasher Air Gaps

A dishwasher air gap is an essential piece of your dishwasher setup. The compact cylindrical fitting consuming space on your sink deck connects the kitchen sink drain to your dishwasher.

Underneath the counter, you’ll find two branches of a hose protruding from this point.

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Purpose of a Dishwasher Air Gap

The sole purpose of a dishwasher air gap is to prevent backflow. Without it, dirty water from your drain could reenter your drain, which is a process called backflow. The presence of the air gap effectively stops this from happening.

By preventing backflow into your dishwasher, the air gap helps keep clean dishes clean, as the dirty water can’t flow back in.

How it Works

The workings of a dishwasher air gap are relatively straightforward. They prevent used water from moving from the drain into the dishwasher by separating the hose into two branches.

The peak of those tubes, which you see above the counter, contains an unpressurized gap of air.

One branch extends back to your dishwasher, while the other connects to your kitchen sink drain or garbage disposal canister.

When the dishwasher pumps dirty dishwater into the hose, it pushes through the air gap of the first hose and flows smoothly into the second hose to reach the drainage site.

Do all Dishwashers Have an Air Gap?

Not all dishwashers have an air gap covered by a metal cylinder on your sink deck. Some models come with integrated air gaps that serve the same purpose without requiring real estate on your sink deck.

Aside from the variations in dishwasher design, there are also differences in plumbing codes. Some states and municipalities require air gaps on dishwashers to prevent backflow problems.

In states that require them, integrated air gaps aren’t an option – it has to be a through-counter air gap.

In other states, adding a through-counter air gap is optional. However, since air gaps serve a vital purpose in preventing backflow, they’re not a bad idea.

Are Dishwasher Air Gaps Necessary?

While helpful, dishwasher air gaps aren’t always necessary. You can create a similar effect using gravity in your favor without pulling the hose branches through the counter to take up space on your sink deck.

To do this, you would reroute the drain hose to the underside of the counter. This places the top of the hose higher than the sink drain, thus using gravity to prevent backflow.

Of course, this might not be a viable option for every homeowner, as some areas require through-counter air gaps.

Other Items By Kitchen Faucets

Sink Sprayer

Dishwasher air gaps aren’t the only thing you might find next to your kitchen faucet.

You might find various faucet accessories, including sprayers, dispensers, filtered water faucets, and cup rinsers.


A sprayer is a handy addition to a kitchen sink layout, especially if your kitchen faucet is noticeably missing a spray head.

A handheld sprayer makes it much easier to clean out your sink, rinse away excess bubbles for washing, or help break away stubborn gunk on dishes.

They sit off to one side of the faucet, resting on a cylindrical lip on the sink deck. The hose extends beneath the sink deck, ensuring it doesn’t crowd your kitchen sink setup.

A simple tug releases the hose from its hiding place, and a quick press engages the water flow from the sprayer. Of course, the faucet needs to be on for the sprayer to work, as it diverts water from the main faucet to itself.


Kitchen Sink Soap Dispenser

Various dispensers might take up the real estate on your sink deck around the faucet. They might hold hand soap, dish soap, or even lotion.

Generally, the bottle containing the liquid of choice is hidden beneath the sink, suspended by threads on the neck connecting to the pump above the sink deck.

Filtered Water Dispensers

The miniature version of your kitchen faucet situated off to one side is likely a filtered water dispenser. These dispensers are ideal for homes with unpleasant-tasting tap water but without a faucet built into their fridge or freezer.

The dispenser generally filters the water on demand, ensuring you can have better-tasting water straight from the tap.

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Cup Rinsers

These fancy accessories are common in coffee shops, bars, and other business settings, but they might also make an appearance in your home.

They feature a circular shape with an open side to direct water into the sink. A grate positioned in the middle of the circle provides a perch for the cup to sit while you rinse.

You simply press the grate down with an upside-down cup to use them. The grate shoots out water, blasting gunk and grime from inside the cup to make cleaning easier. You can even put soap in the cup for a more thorough rinse.

Of course, you’ll still need to clean the cup’s rim, but these can be helpful.

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