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Dishwasher Air Gap Under Counter

Do Dishwasher Drains Require An Air Gap

Dishwasher Leaking Water At Air Gap QUICK FIX

Absolutely. If you have a dishwasher, you should consider installing an air gap. The installation process may sound like extra and unnecessary work, but it will save you big time. It is a small price to enjoy a clean kitchen, a fresh-smelling dishwasher, and good health. Even if your local plumbing codes dont require you to have an air gap on your dishwasher drain, you should install it anyway.

Alternatively, you can install a high loop on your dishwasher drain. In fact, some plumbers will recommend high loops over air gaps based on their experiences with each device. Even so, they both serve the same purpose of protecting your dishwasher from wastewater backup.

Which Is Better: A High Loop Or Air Gap For A Dishwasher

According to experts, an air gap is a better option to protect your dishwasher from the backflow of dirty water. While the high loop can also serve the same purpose, it does not guarantee total protection. As the name implies, a high loop is a drain hose curved in a semi-circle and elevated above the dishwasher drain and the garbage disposal. The elevated loop lies right below the kitchen sink, and this is to ensure that water from the sink drain does not flow back into the dishwasher drain, even if there is a clog.

On the other hand, an air gap is a device that ensures that drain water from the dishwasher does not, at all costs, mix with backup water from the garbage disposal. It is typically a barrier between the two devices, which guarantees the dishwashers safety. Although the air gap is beneath the countertop, its tip lies on top of the counter. Besides preventing the backflow of dirty water, it also maintains adequate ventilation in the plumbing system. In case of a clog in the garbage disposal, water will start leaking through the tiny holes in the air gap into the sink. This will prompt you to clean the drain and prevent any possible damage.

Installing Your Dishwasher Air Gap Steps

Now that you know where to start, we can get into the steps of installing one. Read these steps carefully because you will need a well-finished drainage system.


Step 1: Prepare your workspace

Never start working without knowing what goes where. Preparation is always key to delivering a great job.

The first step is to understand how an air gap works. We have discussed this above already it should not be an issue.

After that, follow these preparation steps:

  • Pull aside parts of the air gap. These include the decorative gap, top cover, top retain nut, counter gasket, and more. Keep the bottom retainer on the gap intact.
  • Set the bottom to retain the nut to meet the sink thickness.

With the air gap separated, you are ready to start the installation.

Step 2: Start the installation

Suppose you are not sure which connection goes where. Try watching online videos that open up these air gaps. It will present a clear view of what is expected.

Step 3: Finish up the installation

You are not yet done. The last and crucial step too is to properly finish up the installation.

You have now successfully installed a dishwasher air gap. Dont forget to try it out and ensure it works perfectly before closing your work area.

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Drainage Blocked By The Clog

With a clogged passage, you can experience water rushing out of the air gap. Check if there is any food debris or any other junk blocking the passage. For that, remove the hose that is connecting the air gap to the drain of the sink by unscrewing the screws that are holding the clamp in place on both sides of the hose. Clean the hose with the help of a stick and you should be done.

Can I Move Airgap Under Countertop And How

The Most Common Dishwasher Installation Defect

I have a single hole faucet in the kitchen with an airgap next to it. Would like to put a soap dispenser in the airgap hole in the counter. I have been told that I can put an airgap under the counter by removing the air gap from the counter, remove the airgap device from the flexible hose and then putting a loop in the flexible hose from the diswasher. It was described that the loop will act as an airgap if its kept up high because the water will drain from that section leaving the required air.

  • 14 years ago

    If a ‘high loop’ is allowed in your area you can put one in.It does not act as an air gap, but is recognized as ‘safe enough’ in many areas.The danger is that a backup into the kitchen sink could flow back into the dishwasher.It is a rather remote possibility given the drain valves used on most dishwashers.

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    Dishwasher Air Gap Under Counter/sink

    To gain maximum benefits of a dishwasher air gap, it needs to stick about 2 inches above the sinks rim. A dishwasher air gap not only prevents backflow of wastewater to the dishwasher but it also ensures that in case the drain hose is clogged, the wastewater will be channeled down inside the sink.

    The air gap also needs to be at a higher elevation than the dishwasher. Even if you manage to install the air gap under the kitchen counter, what will happen when it clogs?

    Wastewater from the dishwasher will spill and flood your kitchen floor. Just have it installed properly.

    The main reason some people opt for a dishwasher air gap under the counter is purely for cosmetic reasons. Most dont like how conspicuous the air gap is adjacent to the faucet.

    You can always think of creative ways to conceal the air gap head if you dont like how it looks.

    Concealed Dishwasher Air Gap

    Is there a concealed air gap available? I really dont want to bore another hole in the new granite counter top.

    Thanks. Darren

  • |#1

    Darren My plumbers usually do not install an air gap at all. They just loop the dishwasher drain hose as high as possible and then down to the drain on the garbage disposal or tailpiece. I have had no problems with such installations and my inspectors don’t complain either.

  • |#2

    ive installed hundreds of dishwashers and have never used an air gap, dont see the need for it

    just make sure the drain hose goes as high as posible before the drain, under the kitchen sink if posible

    dont tie the dw unto a garbage disposal unit either, the soap from a dw is very corrosive and can chew up aluminum in a short time

  • Check with local experts. As others noted, many areas don’t require them. I’ve seen 3 in about 2,000 houses I’ve inspected, and 2 of them weren’t actually connected!?!

    As noted, just high loop the DW drain.


    “I may have said the same thing before… But my explanation, I am sure, will always be different.” Oscar Wilde

  • KARLSTER ||#4

    Double check with your dishwasher manufacturer. A plumber once mentioned to me that most of the european dishwashers have an integral air gap. Unfortunately even if that is the case it can be a challenge to convince the bldg inspector that one isn’t reqd.

    I don’t have an air gap on my maytag and it has not presented any problems.


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    What Is Dishwasher Venting

    Dishwasher venting prevents dirty water from re-entering the dishwasher. There are several common ways to do this: creating a high loop in the drain hose, connecting the hose to an air gap fitting, or installing a check valve on the drain line.

    In any case, it is important to check local building and plumbing codes before installing a new dishwasher. The local code rules dictate the legal requirements in your area. Contact your city’s building department or visit online for more information. In some areas, a high loop is the minimum requirement, but in many other jurisdictions, an air gap must be installed with all new dishwashers.

    Users Who Are Viewing This Thread

    Dishwasher Will Not Drain – High Drain Loop Installation

    Is there such a thing as an undercounter air gap?Is an air gap needed or required if drains to disposal?

    Terry said:The air gap is above the counter.If you don’t have an air gap, at least loop the drain from the dishwasher as high as you can under the countertop before installing to a disposer or a trap.An airgap below the counter isn’t a good idea. They can overflow.

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    Jeff Handy said:I think another problem with the high loop is that if you attach the dishwasher drain hose to a tailpiece with a tee for the drain, and the drain line gets partially clogged, the disposal can try to force gunk back into the dishwasher drain hose.

    both of these will block at the same point for the same reasonthe air gap fitting is not a check valve.i have had inspectors turn a blind eye at the high loop and have had them tell me that after final inspection do what you wanti do not install air gap fittings, but make no mistake, they are code,

    frodo said:NO sir , I beg to differThe air gap is there to prevent the dishwasher from syphoning the dirty water back into the dishwasherby means of an air gap.

    youryourextremely fine

    Dishwasher Air Gap: What Plumbing Codes Say

    If you get a home inspection carried out, chances are high that youll be informed about some sort of issue with the Dishwasher Air Gap. Technicians cant seem to do the installation properly and that area is often ignored. A home inspector can identify the issue and make the correction.

    Some dishwashers do not come with built-in backflow prevention. This is the area where the drain-air-gap device functions it prevents contamination of the interior of your dishwasher. Contamination might occur if theres a sink-drain backup.

    The Plumbing Code says that an air-gap device must be installed at the countertop level in order to stop the backflow to the dishwasher. This device simply prevents the backflow by maintaining the connection up above the flood-level rim and keeping an opening. This device is like a chrome canister.

    The air-gap device comes with a vertical slot which must be directed towards the sink. Sometimes, the air-gap device may fail in sending discharge water through the slot of the air-gap device. In such a case, the air-gap device must be replaced by your plumber.

    Actually, some building codes may allow the high-loop method. This installation may work well in most the cases, except when a siphon occurs.

    Connecting the drain line to the air gap is a method for installing your dishwasher. In certain areas, the building codes say that a dishwasher must be connected to the air gap that is installed on the sink.

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    Do I Need To Install An Air Gap

    The only way to truly prevent all back siphoning in a drain lineis by installing an air gap which requires a decent amount of more work. Some municipalities require air gaps, but most find high loops to be acceptable by themselves. The air gap stops any negative pressure from causing back siphoning into the dishwasher by introducing air into the system. The drain hose connects to the air gap underneath the sink and the air gap sits on the countertop close to the sink. In my experience, most sinks work perfectly fine nowadays with only a high loop installed, but if you are experiencing back siphoning, you may wish to have consult a licensed plumber about having an air gap installed.

    Figure 3: Air Gap Installation

    Is The Air Gap Really Needed For Dishwasher


    Question: The inspector who checked the home were selling reported that the dishwasher needs an air-gap device on the drain line. The problem is that we have no place to install an air gap because the hole on the back rim of the sink is being used for the water purifier.

    Instead of an air gap, our handyman has installed a check valve in the dishwasher drain hose below the sink, but the home inspector says this does not comply with code. The handyman says air gaps and check valves are equally effective and that even a high-loop drain line can be used to prevent back-siphonage. Again, the inspector heartily disagrees. To us, this is a bunch of confusing terminology. Meanwhile, the people who are buying our home insist that this problem be corrected in an approved manner. How do we sort through all of this conflicting technical advice?

    Answers: Your question covers a number of issues and misconceptions regarding dishwasher drain lines. Lets take them one at a time:

    * An air gap typically appears as a small chrome cylinder commonly found on the back rim of most kitchen sinks.

    It is what plumbers call an anti-backflow device because it prevents sewage from flowing back into the dishwasher. Your inspector was correct in recommending that an air gap be installed. Although alternative methods are available, only an air gap is approved by the plumbing code, because it is the only method guaranteed to work in all circumstances.

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    How To Clean Air Gap

    To clean an air gap, first remove any debris from the opening. Then, use a soft cloth or brush to gently clean the surfaces around the gap. If the air gap is particularly dirty, you may need to use a mild cleaning solution. Be sure to rinse the area well and dry it completely before replacing the cover.

    Are Dishwasher Air Gaps Always Necessary

    You absolutely do need to have a way to prevent backflow from happening with your dishwasher, and air gaps are generally seen as the most reliable option out there. Most jurisdictions will require you to install an air gap wherever you want to place a dishwasher.

    However, you do not need an air gap. There are a small handful of alternatives that you can grab in order to keep your air gap sanitary.

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    High Loop Dishwasher Connection

    In the high loop method, the drain line of the dishwasher is looped up as high as possible under the countertop before it runs back down to connect to the drain system. In some areas, this high loop method is an allowable option, but make sure to check. Because the top of the loop is located above the flood level of the dishwasher, it makes it unlikely that drain water can be siphoned back into the dishwasher.

    The high loop method is not as reliable as an air gap, but it can help to prevent contaminated water from being drawn back into the dishwasher. Where allowed, the high loop method frees up a sink mounting hole that can be used for a soap dispenser, water filtration, or instant hot water dispenser.

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    What Is The Purpose Of A High Loop

    Dishwasher Leaking on Counter – Easy FIX

    A high loop prevents waste water back flowing from your sink to your dishwasher. If the drain hose is not elevated, there is a potential for water to run the wrong way through your drain hose and can cause standing water at the bottom of your dishwasher. The high loop also protects mild cases of back siphoning due to increasing the hydrostatic pressure that the water needs to overcome to get over the loop.

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    How To Install A Dishwasher Air Gap Under The Countertop

    Last Updated on September 13, 2022 by Peralta

    If you have been using a dishwasher for a long time, you may have, at some point, experienced a wastewater backup. While this is the worst that can happen, even a mere smell of sewage in your dishwasher wont be a pleasant thing to experience. The good news is that you can prevent such from happening, and thats where a dishwasher air gap comes in handy. This small device protects your dishwasher from any wastewater that may back up just in case the kitchen-sink drain or garbage disposal clogs. This article outlines the step-by-step process of how to install a dishwasher air gap under the countertop. Stay tuned.

    What Is A Dishwasher/sink Air Gap

    If you are installing a dishwasher or already have one but without an air gap, you need to install one. Not only is a dishwasher air gap required by code, it is the most effective way of preventing backflow and contamination of your dishwasher when the drain line clogs.

    Before air gaps became common, dishwashers were plumbed by looping the drain hose high underneath the countertop. That method has little success in preventing wastewater backflow to the dishwasher. More on this later on in this post.

    If water from your sink is going into the dishwasher, you have a clogged sink drain line or garbage disposal. To fix this problem, you will need to unclog the sink drain and install an air gap to prevent the same from happening in future.

    But what is a dishwasher air gap and how does it work? Do you even need one?

    A sink/dishwasher air gap is a fitting installed between the dishwasher drain hose and the sink drain line/garbage disposal to prevent backflow, contamination and an overflowing dishwasher.

    The top of the air gap has a finished cap and pops 2 inches above the sinks rim. In case of a clogged drain line, the air gap prevents the wastewater from being siphoned back to the dishwasher.

    One thing to remember is that the dishwasher, garbage disposal and sink share the same drain line. This means that if there is a problem with one of the 3, all the others will be affected. That is the reason you will see water backing up to your sink when running a dishwasher.

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