What is the thing next to my kitchen faucet?

Author: Oswald Mante  |  Last update: Saturday, February 7, 2026

“That thing” is actually called an air gap, and it prevents wastewater from siphoning back into the dishwasher, which can occur when sinks become clogged and no air gap is present. Without an air gap, contaminated water could be sucked back into the dishwasher, dirtying your clean dishes and making you ill.

What is the little thing next to kitchen faucet?

The valve is actually for the dishwasher and is commonly known as the dishwasher air gap. An air gap's purpose is to prevent drain water from the kitchen sink backing up into the dishwasher, contaminating your cleanly washed dishes. Now that you know what it is, how does it actually work?

What is the purpose of the kitchen air gap?

A dishwasher air gap is a cylinder fitting that connects the kitchen sink drain to your dishwasher and prevents dirty water from entering your clean dishes. It also prevents water from flowing back out during a cleaning cycle.

What is the thing by my kitchen faucet?

The metal thing in question is a small, cylindrical metal tube that sits next to the faucet on your kitchen sink. Reddit user @dominostracker wondered the exact same thing, and according to a few wonderful human beings who took the time to answer, that thing is an air gap.

What is the vent on my kitchen sink?

Essentially, kitchen sink vents allow air to circulate, and as a result, equalizes pressure in the kitchen drain pipes. This helps sewage flow more effectively by reducing clogs. The kitchen sink vent also prevents odors from flowing back into the kitchen, thereby keeping it smelling clean and fresh.

Choose the Right Kitchen Faucet and Sink: Good Better Best

How do I know if my sink vent is clogged?

Signs of a clogged vent include slow-draining fixtures, gurgling sounds in the plumbing, or sewer gas odours around sinks and drains. A clogged vent is often located on the roof, but it can sometimes be obstructed lower down the line as well.

What does an air admittance valve do?

The air admittance valve (AAV) is a device designed to allow air to enter the drainage system to balance the pressure and prevent siphonage of the water trap when negative pressure develops in the system.

What is that thing next to the kitchen faucet called?

“That thing” is actually called an air gap, and it prevents wastewater from siphoning back into the dishwasher, which can occur when sinks become clogged and no air gap is present. Without an air gap, contaminated water could be sucked back into the dishwasher, dirtying your clean dishes and making you ill.

Is an air gap necessary?

Air gaps are the most effective means of preventing your drain from contaminating your dishwasher with waste. If you want to protect your dishwasher from flooding with contaminated water, you need an air gap.

What does a kitchen faucet aerator do?

The purpose of an aerator is to conserve water while using the faucet longer, and without it, a stream of water can flow faster and more freely. Sink aerators are standard components on nearly all kitchen and bathroom faucets, but like any other piece of equipment, they need to be maintained every once in a while.

What does a kitchen sink air gap look like?

The air gap resembles a short, squaw cylinder that may appear to have open valves on one or both of its sides. Your sink faucet sits several inches higher than your sink rim to protect against sink water overflowing to the point that it could re-enter the faucet line where your clean water comes from.

What is a faucet air gap for?

Air gap faucets have their advantages and disadvantages. The purpose of the air gap is to assure that no water from a stopped-up sink drain can possibly be forced or siphoned backward into your reverse osmosis unit via its drain connection.

Should water come out of the air gap?

Your dishwasher does more than clean your dishes; it is an important part of maintaining your family's health. One way it does that is by draining away wastewater through the air gap. When your air gap leaks, it indicates a problem.

What is a kitchen faucet diverter?

A faucet diverter valve is a plumbing mechanism that lets you “divert” (or redirect) water from your bathtub faucet to your showerhead and back. You can also use it to switch back and forth between the kitchen faucet and the faucet sprayer. In either case, it allows water to be diverted from one spout to another.

What is the build up around my faucet?

Calcium buildup is also called limescale. This happens because water that contains dissolved calcium salt is flowing through your showerheads and faucets. This is why you have that white crusty-looking buildup that is all but impossible to clean away.

What happens if you don't install an air gap?

What If My Dishwasher Has No Air Gap? Without a dishwasher air gap, contaminated water can flow back into the dishwasher. A dishwasher air gap prevents this from happening by ensuring that the water flows in one direction: out of the dishwasher and into the garbage disposal.

How much does it cost to replace an air gap?

How much does a Air Gap cost? A typical price for a Air Gap is $25 but can range from approximately $6 to $39. What are the most popular color/finish families of Air Gaps? Stainless steel, Black and Chrome are among the most popular colors of Air Gaps.

Does every sink have an air gap?

No. An air gap is basicly a mini air vent stack for your dishwasher. If no dishwasher is installed then no air gap is required for the sinks to drain properly.

What is a faucet escutcheon plate?

An escutcheon is a pretty metal piece used to hide a hole in your wall where a pipe comes through. They can be found behind your faucets, showers, toilets, and under your sink.

Can water come out of an air admittance valve?

In order for a liquid to come out, air must come in. All DWV plumbing systems require at least one vent penetration through the roof line, which allows air to enter the system, while also permitting sewer gas to escape.

How to tell if an air admittance valve is bad?

Another way is field testing in a cup of water, Place the air admittance valve (AAV) in a cup as shown below. This creates a positive pressure which seals the membrane and allows the valve to float. If the AAV sinks then most likely the membrane has been compromised which allows air to pass through the AAV and sink.

What is the life expectancy of an air admittance valve?

Air admittance valves have a typical life expectancy of 20-30 years, so if you start to have issues with sewer gases or smells being released around your sink or in the attic-wherever installed- the air admittance valve could be faulty or failed and should be replaced as soon as possible.

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