Dishwasher Air Gap Leaking Under Sink  


If you’re like most people, using the dishwasher is a pretty important part of your daily routine. You load it up, turn it on and walk away. But like with any appliance, there will be problems and inconveniences. A leaking air gap is normally a very easy fix. Typically if your air gap is leaking there are three potential problems. The first being the drain hose has became lose, second because of a clog in the air gap and lastly because of a faulty air gap.

The air gap serves the purpose of making sure that dirty water will not make its way back into your dishwasher after draining. It is a key piece in the functionality of your dishwasher.

Before calling a plumber or dishwasher repair company, you may be able to troubleshoot and fix the problem yourself. In order to understand how to tackle this repair work, it’s useful to understand a bit about the air gap and its important function.

What is the Purpose of a Dishwasher Air Gap?

The air gap of your dishwasher works to prevent contaminated water from getting back into the dishwasher. Without it, there would be no way for the dirty water in the dishwasher to drain properly. The last thing you want is for wastewater and contaminants to dirty your clean dishes.

How it works is that waste water enters a tube that runs from the dishwasher to the air gap (which is known as the drain line). From there, the water goes into a tube that drains into your garbage disposal or directly into the drain pipe (which is the pipe under your sink connected to the drain). Due to this air gap, backflow and cross-contamination are impossible unless there is a clog.

Components of the Air Gap

The air gap consist not only of the air gap its self but also two hoses and hose clamps. You will need to verify which size of hose to use depending on the size of the required for your specific air gap model. Most commonly they are 7/8″ and 3/8″.

These clamps are used to secure the hoses onto the air gap but also into the drain/garbage disposal but also into the dishwasher its self.

Location the Air Gap

In most instances, the air gap is easy to locate. It’s that silver, metal fitting that is usually located near the faucet on your sink. The air gap is best to be located on the sink because if there is a backup in the garbage disposal or sink drain the water will be pushed out of the top of the air gap back into the sink.

They can also be located on your counter but this is not the smartest location for it because if there is a clog then water will spill onto your counter top.

Some dishwashers do not have this type of air gap, but many states require one according to code. Air gaps are great because if there is a clog water will run into the sink and not under the sink if there is a problem.

What Can Cause The Air Gap To Leak?

The most common causes of an air gap leaks:

  1. A clog in the air gap or somewhere near it. This clog could be in either the hose leading from the dishwasher to the air gap, or it could be in the hose going to the garbage disposal or sink.
  2. Lose connection of the drain hose to the air gap.
  3. Broken or faulty air gap, or there could be a leak in one of the drainage hoses.

How To Check For Clogs And Remove Them Safely

If you think that the issue stems from a clog in your air gap, then there are some steps you can take to resolve the problem without the need to call in the professionals.

Step 1: Unhook the Drain Hose

In order to unhook the drain hose which is connected to the air gap you need to access it. Make sure to turn the power off and to unhook the electrical wiring so you do not rip out any wiring.

Once you have unhooked the dish washer and pulled it away from the wall you should be able to access where the drain hose connects to the sump pump. You can then disconnect the drain hose pretty easily.

Step 2: Locate Clog

After you have unhooked the dish washer and the drain hose you can remove the metal covering from the air gap. There will be a plastic fitting where you can squeeze the tabs on the top of the air gap and remove it.

You will now see two holes, the smaller hole is where water from the dishwasher enters the air gap. The larger hole takes that water and brings it to the garbage disposal or sink drainage pipe. Visibly check these holes for debris. If you don’t see any obvious clog, take a piece of plastic tubing and push it into the larger hole. Gently work this tubing down the hole. If there is a clog there, you should be able to feel it shift. Put the dishwasher on the drain cycle. If the clog is gone, there won’t be any more water leaking into the sink.

Step 3: Vacuum Line or Blow Air into Air Gap

A wet-dry vacuum can also be used to gently suck the debris from the air gap itself. Remove the metal cover to the air gap. You should see a plastic cover with tabs. Squeeze the tabs and remove this plastic cover. Now place the hose portion of the vacuum over the air gap. Let it run for about a minute. That should remove the clog.

You can also take the cap off the air gap and put paper towel or a cloth over the top part of the mechanism. take a deep breath and exhale as hard as you can where the cloth is placed over the holes of the air gap.

Side Note: Another issue could be with the knock-out plug in the garbage disposal. If you have a new disposal, and the knock-out plug was not removed, this could definitely be your problem. This plug can be found where the hose to the air gap meets the garbage disposal. Once you locate the knock-out plug, carefully take a screwdriver and hammer and gently remove this plug. This should do the trick if the issue didn’t stem from a clog.

How to Spot and Fix Air Gap Leaks

Maybe you have already tried the above steps, and you are still having issues. It would be safe to conclude at this point that the problem most likely stems from a leak in one of the hoses. If done properly, this is something that you can safely and easily fix yourself.

Step 1: Locate the Leak

Turn the dishwasher to the drain cycle and look at the hoses that run under the sink. Look carefully for any leaks. If you see any leaks, circle them with a marker. For leaks that are not visible, you can take a paper towel and rub it on the hose. Use your maker where you feel wetness.

Step 2: Patch Hole

The next step is to apply epoxy putty on the spots you circled with the marker. Make sure to put on enough putty to cover the circle by at least an inch. Let it dry for 24 hours, and you should be good to go. You can try running the dishwasher on the drain cycle one more time to be sure.

Fully Replace Air Gap and Drain Hose

If there was no clog in the air gap and you could not effectively locate and patch the leak you will need to replace the air gap.

You will need to purchase:

  1. Air gap
  2. Drain hoses
  3. 4 Stainless steel hose clamps

Steps to Installing an Air Gap

Step 1:

Unhook the drain hose from where it is connected to the drain or garbage disposal.

Step 2:

Remove the power and unhook your dishwasher and pull away from wall.

Step 3:

Take the cover off of your new air gap.

Step 4:

Attach the appropriate size drain hose to to the nozzle that will be hooked into the dishwasher. The hose will most likely be 5/8″. Use a stainless steel clamp to tighten the hose onto the air gap.

Step 5:

Attach another hose to to the outlet on the air gap. This hose will be the drain line that is connected either above the P-trap or directly into the garbage disposal. This hose should be 7/8″. Use a stainless steel clamp to tighten the hose onto the air gap.

Step 6:

With the hoses attached to the air gap inlet and outlet insert the air gap through hole in sink or counter top. Make sure that you use a washer in between the nut that tightens against the under side of the counter.

Step 7:

Tighten the nut and washer on the top side of the air gap to hold the mechanism in place. Place the cover back onto the top of the air gap.

Step 8:

Attach the 7/8″ hose directly into the garbage disposal or the P-trap. Make sure to use another stainless steel clamp to tighten the hose in place. It is important to make sure that the hose does not sag below where it is connected or it will not drain properly.

Step 9:

Attach the 5/8″ drain hose into dishwasher. You will be able to attach the drain hose directly into the sump pump. Make sure to use a stainless steel clamp on the drain hose to make sure no water can escape.

Here is a good video showing these steps visually:

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