Dishwasher Air Gap Leaking Under Sink

Dishwasher Air Gap Leaking Under Sink-Potential Causes

The phrase “dishwasher air gap” may not be recognizable to you, but you’ve probably seen one before. Typically, a decorative cap is placed over the dishwasher air gap once it has been attached to an existing hole in your sink or countertop.

The air gap enables your dishwasher to pump soiled water out of its system and bring in clean water by connecting to hoses running beneath your sink and leading to a drain pipe.

But sometimes your dishwasher air gap starts leaking due to an uncertain cause. Let’s dig into this article to find out some potential causes of dishwasher air gap leaking:

Why Is Dishwasher Air Gap Leaking Under Sink?

The air gap located at the sink’s countertop level is often where the dishwasher’s drain line joins. From the air gap, the drain line continues to either the garbage disposal or the sink drain.

But sometimes the dishwasher air gap starts leaking under the sink. This happens when water from the dishwasher will spill out of the air gap and into the sink if the drainage line that connects the air gap to the drain is partially or totally blocked.

Simply remove the hose, flush it out, or replace it to clear the obstruction. Check the dishwasher inlet of the garbage disposal to make sure it is clear when the hose is disconnected.

Check the garbage disposer knock-out plug if the dishwasher or garbage disposal has just been replaced. Before utilizing the dishwasher, the stopper at the connection between the drain line and the garbage disposal must be removed. If it isn’t removed, the water won’t be able to drain correctly and will leak out of the air gap.

Different Dishwasher Air Gap Types

Finding the trouble spot is the first step in repairing a leaky dishwasher, just like with any other appliance. You must analyze the problem in order to accomplish this. To diagnose your leak and determine how to remedy it, follow the procedures listed below.

There are two primary types of air gaps for dishwashers,:

  • Under-sink air gaps
  • Countertop air gaps

The most typical are countertop air gaps. These come with a beautiful cover and can be found on your sink next to the faucet or behind your countertop. An alternative location for a dishwasher air gap is under your sink, close to your garbage disposal (if you have one). To achieve optimal efficiency, some dwellings might even feature two air gaps, one in each location.

A Dishwasher Air Gap: How Does It Operate?

One of the best methods for defending your dishwasher from backflow is using dishwasher air gaps.

  • Two branches that are split by a piping break make up an air gap. From the dishwasher drain up to the air gap external fixture, the inlet branch rises and curves. Following the break, the pipe system is carried on by the second branch, known as the output branch. This branch is often the larger of the two.
  • Through the input pipe, the water rises from the dishwasher. It ascends the pipe under pressure. Gravity then transports it past the air gap and into the outlet pipe leading to the drain after it loops over.
  • Pressure is what causes the drained water to ascend up the outlet pipe once more, resulting in backflow. However, gravity cannot get it into the inlet branch since the inlet pipe is looped over the outlet pipe. Additionally, the air gap prevents pressure from bringing it into the inlet branch.
  • Instead, the backflow spills into the kitchen sink via the metal lid and escapes through the air gap.

Why Is An Air Gap Required In A Dishwasher?

Your kitchen’s plumbing system receives the runoff from your dishwasher. Even though the drainage system normally runs smoothly, there is a remote possibility that some of the contaminated water will back up into the dishwasher and re-dirty the dishes that have just been washed.

Additionally, some of that contaminated liquid can make its way into the clean water stream that is pouring from your faucet.

You must make sure that the dishwasher’s drain pipe has an air gap in order to prevent this form of contamination.

Building codes in most regions mandate this, therefore it is not a choice. The component that is easily seen usually resembles a tiny cylinder and is frequently silver chrome in color. You’ll see it located at there is the edge of a typical kitchen sink.

Potential Issues Caused by No Air Gap

You are leaving your dishwasher vulnerable to wastewater backups if there is no air gap or other backflow prevention measures in place.

Despite the fact that dishwashers include traps that are meant to prevent backflow, they can malfunction if they become dry.

A health risk arises from the dishwasher’s wastewater presence. It may produce microorganisms that provide a health risk, such as gastrointestinal problems.

Standing wastewater can promote the development of mold and mildew if left unchecked. It would also result in the dishwasher emitting an unpleasant smell.

Furthermore, the dishwasher would need more time to wash dishes if there was standing water present. You would be using more electricity than necessary if you run the dishwasher for longer.

What Does It Mean When Water Comes Out of an Air Gap?

The most frequent reason for water to leak from an air gap is a blockage in the water’s path to the garbage disposal. Although it indicates a plumbing issue, it also indicates that your air gap is in good operating order!

These factors may lead to obstructions:

Kinks In The Discharge Hose 

The presence of kinks in the discharge hose would restrict water flow and could even lead to food and debris settling and finally clogging the pipe.


Debris and food particles may become lodged in the drain pipe or tubing, obstructing the free passage of water into the drain. Clogs in the drain hose that carries water from the air gap to the garbage disposal are the main source of air gap water leaks. Clogs in the air gap tubing may possibly be the reason for it.

Install new garbage disposals with a bang

You must unplug the plug at the dishwasher outlet on new garbage disposals before connecting the hose. Water would be unable to enter the garbage disposal if the knockout plug was left in place, and it would instead be forced to drain out the top of the air gap.

Substitutes For The Dishwasher Air Gap. 

You also need to be aware of air gap choices if you want to install a dishwasher in your kitchen.

An air gap shields the dishwasher from contamination and stops drain water from backing up. You should be informed of the requirement for an air gap when installing the dishwasher.

There are various excellent substitutes for the air gap, which was useful in preventing wastewater from reentering the dishwasher.

You must install the dishwasher with an air gap, as advised by various building codes. There are three excellent alternatives to airgaps: the high loop, the standpipe, and the check valve. Continue reading to learn more about each one in depth.

Consider A High Loop.

The most popular substitute for a dishwasher air gap and the best technique to manage water backflow is a high loop.

In a high loop, the drain hose is positioned below the sink level and extends above the water line in a special design. It can be connected to the garbage disposal or the drain. It functions according to gravity and the fundamentals of physics.

By including this substitute, the water backflow into the dishwasher is reduced. The high loop’s best feature is that it doesn’t need any specialized tools or components. The only thing you’ll need is some brackets or hooks to hold the drain hose in place.

An Option Is A Check Valve.

Consider the check valve as an additional air gas substitute for dishwashers. A check valve is a piece of hardware that ensures water or any other liquid flows exclusively in one direction.

The check valve conveniently handles water backflow and stops drain water from entering the dishwasher without the need for any additional hardware to be put in the kitchen area.

Near the drain pipe on most dishwashers is a built-in flap check valve. Prioritize avoiding the use of check valves; but, in emergency situations, they may be necessary.

Setting Up A Standpipe

Consider a standpipe as a form of a long pipe that is typically found at the P-trap section of the plumbing unit. It is a kind of long pipe that may be thought of as a potential replacement for the air gap. A diameter of about two inches should be taken into consideration for the dishwasher’s ventilation.

The standpipe also has the virtue of accelerating drainage while also closing the air gap, which is a good advantage. The addition of a second standpipe under the sink aids in preventing backflow and maintains ventilation for the dishwasher.

Although a standpipe is not the greatest option for an air gap replacement, it is an expensive method that necessitates a lot of plumbing steps.


Is it normal for water to come out of the dishwasher air gap?

If someone forgets to run the garbage disposal, for example, water may occasionally come out of the air gap, but it shouldn’t happen frequently. An air gap’s regular water discharge suggests that there is a restriction in the water flow.

Why is water coming out of my sink air gap?

The state of the supply water at the moment can be causing an air gap leak. The likelihood of accumulating debris increases with feed water contamination and dissolved solids. When something obstructs water flow, air holes reopen. Debris may build up in the air gap of your RO system as a result of a slow-moving sink drain.

Why is my dishwasher leaking under the sink?

It is most likely coming from the disposal or the air gap. Replace the damaged hose and tighten the hose clamps once more. It’s possible that some of the water flowing from the air gap on top of the sink makes its way into the cabinet.

How do you fix a leaking air gap?

Remove the air gap cap for milder clogs, then cover the hole with a cardboard tube from a roll of paper towels. Any stuff should fall loose if you forcefully blow through the top. However, you can also use a wet/dry vacuum or a long bottle brush to fix the problem if this doesn’t work.


To guarantee that your dishwasher is operating properly and to protect your health and hygiene, dishwasher air gap leaks must be fixed. Get the assistance of an appliance repair specialist to remedy the problem if you are having issues doing this troubleshooting.

If left untreated, dishwasher air gap leaks can cause more damage than just a leak. The air gap is a crucial element for maintaining the dishwasher’s cleanliness. Therefore, as soon as you notice the leak, resolve this issue by troubleshooting it.