What Is an Air Gap in Plumbing? Everything You Need to Know

Last Updated On June 11, 2024

Updated on July 18, 2022



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What Is an Air Gap in Plumbing

An air gap is an important part of the plumbing system that helps to prevent water contamination. It is a physical separation between the drain pipe and your potable drinking water. This article will explain what an air gap is, what it does, and how to install one in your home!

In this PlumbingNav guide, we will cover:

  • What is an air gap?
  • How does an air gap work?
  • How to create an air gap
  • Troubleshooting an air gap

What's In This Guide?

      What Is an Air Gap?

      An air gap is a physical separation between the non-potable water plumbing system and the potable water supply. This separation helps to prevent water contamination, and it is required by the plumbing code for a wide variety of plumbing fixtures. It’s the highest form of backflow prevention for a plumbing fixture.

      A dishwasher air gap is one of the most common examples you’ll run into. However, air gaps can be found at the end of a water line where contamination is more likely in many different places, such as:

      • Around electrical wires
      • Between the floor and walls
      • Crawl spaces
      • Attics
      • Dishwasher
      • Sinks/ garbage disposal
      • Water heater
      did you know what is an air gap in plumbing

      Air gaps help to keep water from contaminating the water in these areas. They also help to keep pests out of these areas. That’s why air gaps are an important part of any plumbing system.

      Installation of an air gap is not difficult, but it is important to follow the manufacturer’s instructions carefully. Improper installation can lead to serious problems, such as:

      • Water contamination
      • Sewer gas
      • Flooding
      • Pest infestation

      Did You Know? Drain flies occur when you allow standing water to remain in your pipes. However, drain flies don’t bite, and you can take steps to quickly get rid of drain flies.

      How Does an Air Gap Work?

      An air gap is not airtight, but it does provide enough resistance to prevent contaminated water from being sucked back into the clean water supply. 

      What is an example of an air gap in plumbing? A basic example is the space between your kitchen sink faucet and the sink rim is an excellent example of how air gaps work. With no intersection, it’s impossible for dirty water running through the sink drain line to end up back in another water pipe!

      The most common air gap in plumbing relates to the dishwasher. Notice that thing sticking out of the back of your sink, that’s too short to be a faucet and not a handle? That’s an air gap. 

      Waste water is pumped out of some appliances and carried by a hose, and air in the system is crucial to the proper function. The water outlet from the sink hose or dishwasher hose in the air gap is higher than the opening to the drain hose, and this facilitates the needed pressure.

      How to Create an Air Gap

      There are a few different ways to create an air gap, but the most common method is to install an air gap device. The two most common air gap fittings are a tee fitting or a vacuum breaker.

      You can install a Tee fitting on the incoming water line. This fitting allows air to enter the system through a small hole, while still keeping the water flowing in the opposite direction. 

      Another way to create an air gap is to install an atmospheric vacuum breaker on the outgoing pipe. This device breaks the vacuum that can form in the pipes, and it also allows air to enter the system. 

      Either of these methods will create an air gap that will help to keep your plumbing system running smoothly.

      You can also find an air gap faucet that includes an air gap already.

      When sizing the air gap, the vertical distance between the supply pipe and the flood level should be two times the diameter of the supply pipe with a minimum of 1”.

      Troubleshooting an Air Gap

      If you notice water coming out from your air gap, the first thing you should do is check to see if the air gap is clogged. 

      To do this, simply remove the cap from the air gap and look inside. If you see any debris or buildup, use a paper towel or other soft cloth to gently clean it out.

      Once you’ve done this, replace the cap and run some water through the air gap to see if the problem has been resolved. 

      If water still comes out, or if the air gap seems to be leaking, contact a plumber or other professional for assistance. While they are there, consider making the most of their time under the sink since plumbers can quickly install a new garbage disposal while fixing an air gap.

      See the video below on troubleshooting a dishwasher air gap:

      Frequently Asked Questions About Air Gaps in Plumbing

      How does an air gap work?

      Air gaps work by putting a buffer in between different hoses, ensuring that dirty water can’t return into your pipe.

      Why is water coming out of my air gap?

      If you notice water coming from your air gap, it’s most likely clogged. You will want to clear the air gap. 

      How do you clear an air gap?

      To clear an air gap, simply open the cap and remove any buildup. It’s as simple as that.

      Related: See this post if you’re wondering what a plumbing riser is!

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      We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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