Dishwasher Air Gap Leaking? Why and How to Fix It

A dishwasher air gap is a simple but very efficient fitting used to prevent wastewater from siphoning back to the dishwasher in case of a clogged garbage disposal or sink drain line.


To fix a leaking dishwasher air gap, disconnect the drain hose from the garbage disposal and then snake it or blow air from the top. If the problem is caused by a dishwasher knockout plug, knock it out with a hammer and punch and fish it out with a pair of tongs.

Here is a brief summary of this post:


  • Clog or Blockage: Accumulated debris or food particles in the air gap can obstruct the flow of water, causing it to leak.
  • Improper Installation: An incorrectly installed air gap, such as one with loose connections or an incorrect height, can lead to leaks.
  • Cracked or Damaged Component: Over time, the air gap’s plastic or metal components, including the cap or the body, may become cracked or damaged, causing leaks.

How to Fix It

  • Inspect for Clogs: Begin by removing the top cap of the air gap. Check for any clogs or blockages in the air gap’s components. Clean any debris you find and reassemble the cap.
  • Check the Drain Hose: Ensure the dishwasher’s drain hose is properly connected to the air gap and that there are no kinks or blockages in the hose.
  • Proper Installation: Verify that the air gap is correctly installed. It should be mounted above the sink or countertop with the drain hose connecting to it and another hose running from the air gap to the disposal or drainpipe.
  • Tighten Connections: Check all hose connections, including those to the air gap, the dishwasher, and the disposal or drainpipe. Tighten any loose connections securely.
  • Inspect for Damage: Examine the air gap’s components for cracks or damage. If you find any, replace the damaged parts with new ones. You can often find replacement kits at hardware stores.
  • Clear the Drainpipe: If the air gap connects to the disposal or drainpipe, make sure that these components are clear of blockages or clogs.
  • Run a Test Cycle: After making these adjustments and repairs, run a dishwasher cycle to check for leaks. Keep an eye on the air gap and the connections to ensure they are watertight.
  • Professional Help: If the issue persists or if you’re uncertain about the cause or the fix, consider consulting a professional plumber or appliance repair technician for a more in-depth assessment and repair.

How It Works

As I have already mentioned, a dishwasher air gap prevents wastewater from being siphoned back to the dishwasher in case of a clogged drain line. But how exactly does it do that?

Most people only know the dishwasher air gap as a small protrusion next to the faucet but never really care much to know how it works. What is above the sink is only a small piece of the whole fitting. The bigger part is underneath it.

A dishwasher air gap looks like an inverted Y. It has 2 branches, although dual inlet dishwasher air gaps have 3 branches which allow you to install 2 dishwashers or a dishwasher and a water filtration system.

The ascending branch is where the dishwasher drain hose is connected to while the descending branch is where the drain hose connecting to the garbage disposal is attached to.

The vertical section of pipe is the actual air gap. According to physics, water cannot be siphoned back through an unpressurized gap of air.

This means that if the garbage disposal or sink drain line are clogged, wastewater will back up through the sink drain but cannot be sucked back to the dishwasher. This is the main advantage of an air gap over a high loop.

When wastewater from the dishwasher reaches the top of the air gap, it falls down through the other branch via gravity and enters the garbage disposal.

Food particles and grease will accumulate inside the drainpipe over a period of time resulting in a clog. It does not even have to be a full clog.

Partial clogs (which will develop into full clogs if not removed) will restrict the passage of wastewater from the dishwashers forcing it to shoot from the top of the air gap and drain into the sink.

If the clog is in the first branch of the air gap, you will notice that the dishwasher will not be draining resulting in flooding.

How to Fix It

Before starting fixing the problem, you should start by first turning off or better still unplugging the garbage disposal from the electrical outlet.  Electricity and water don’t coexist so this is to protect you from electrical shock.

1. Blow into the Air Gap

Now that the area is safe to work on and you know where the problem is, unclogging a dishwasher air gap is very easy.

  • Start by popping off the top of the air gap.
  • Remove the cap. Look for 2 tabs on the air gap and press them in and lift off the cap
  • Grab a paper towel roll and place it over the air gap and press down on it firmly to create a tight seal.
  • Place you mouth over the top of the paper towel roll and forcefully blow air into it.

For light clogs, the air pressure is usually enough to dislodge it and force it into the garbage disposal.  Run your dishwasher again and check if the problem has been fixed.

2. Snake the Air Gap


If you have a sink snake, you can also use it to remove the clog.

  • As you will notice, there are 2 holes on the air gap. There is an outer one and an inner. You want to snake the air gap from the outer hole.
  • Insert and push the snake inside the air gap until you encounter resistance. Twist and turn the snake until you break down the clog.
  • Run the dishwasher and confirm that the clog has been removed.

3. Inspect the Drain Hose

If the above methods don’t fix the problem, try disconnecting the drain hose from the garbage disposal and removing the clog physically. Most of the times, the clog is located where the drain hose is connected to the garbage disposal.

  • Grab a screwdriver and disconnect the drain hose from the garbage disposal.
  • Stick the screwdriver inside the garbage disposal to check if the drain opening is clogged. With a new garbage disposal, you will also need to check if the knockout plug was removed during installation.
  • If the garbage disposal opening is not clogged or plugged, inspect the inside of the drain hose for clogs. Insert a thin snake through it and pull out as much gunk as possible.
  • Connect it back to the garbage disposal and run a cycle to see if the problem has been fixed.

4. Remove the Garbage Disposal Knockout Plug

Garbage disposals are sold with the dishwasher connection already plugged. This is because there are some people who will want a garbage disposal but do not have or do not need to connect it to a dishwasher.

While connecting the dishwasher drain hose to the garbage disposal, you are supposed to knock out the plug. If you have checked and found that indeed the knockout plug is present in your garbage disposal, look for a hammer and punch or screwdriver.

Insert the punch or screwdriver inside the garbage disposal drain opening and punch it gently using the hammer until the plug drops inside the disposal.

Since you cannot run the garbage disposal when the plug inside, use a pair of tongs to fish out the plug.

And basically that is how to fix a dishwasher air gap that spurts water when the dishwasher is running.

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