How to Clean a Dishwasher Air Gap: Step-by-Step

What is an air gap?

An air gap is a small device, usually made of chrome or plastic, that sits on your countertop near the sink. It looks like a small cylinder with a cap that has two small holes. It is connected to the dishwasher drain hose and to the sink drain or garbage disposal. Its purpose is to create a physical break in the drain line, preventing wastewater from siphoning back into the dishwasher. This is a critical safety feature that protects your dishwasher from contamination and your dishes from dirty water.

The air gap is often required by local plumbing codes. When your dishwasher drains, water is pumped out through the air gap and into the sink drain. The air gap ensures that even if there is a backup in the sink drain, the water cannot flow back into the dishwasher because it would have to rise above the air gap opening and spill onto the countertop instead. This is why you sometimes see water leaking from the air gap when it is clogged or when the sink drain is blocked.

If your dishwasher does not have an air gap, it may use a high-loop drain configuration instead. In that case, the drain hose is looped up high under the countertop and then down to the drain. This also prevents backflow, but it is not as foolproof as an air gap. To learn more about the different drain methods, see our guide on dishwasher drain options.

Why does an air gap clog?

Over time, food particles, grease, soap scum, and even small debris like seeds or bits of plastic can accumulate inside the air gap. The narrow passages inside the device are only about a half-inch in diameter, so it does not take much buildup to restrict flow. When the dishwasher drains, the water has to push through this debris, and eventually the passage becomes blocked.

Hard water can also contribute to clogs. Mineral deposits from hard water can coat the inside of the air gap, narrowing the opening further. This is especially common in areas with high mineral content in the water supply. If you have hard water, you might need to clean the air gap more frequently.

Another common cause of clogging is running the dishwasher without scraping dishes properly. While modern dishwashers are designed to handle some food waste, large chunks can get through the filter and into the drain line. That is why it is important to scrape off large food scraps before loading. For more on loading habits, see our how to load dishwasher for best cleaning guide.

Signs of a clogged air gap

How do you know if your air gap is clogged? The most obvious sign is water leaking from the air gap cap or from the base of the device while the dishwasher is draining. This happens because the water cannot flow through the air gap fast enough, so it backs up and overflows.

Another sign is that your dishwasher does not drain completely, leaving standing water at the bottom of the tub. You might also hear a gurgling sound from the sink drain or notice that water is slow to drain from the sink. Sometimes you will see a bad odor coming from the air gap, which is a sign that food particles are rotting inside.

If you notice any of these signs, it is a good idea to clean the air gap as soon as possible. Ignoring the problem can lead to more serious drainage issues and even leaks that can damage your countertop.

Tools and materials you will need

Cleaning an air gap is a simple task that does not require specialized tools. Here is what you will need: a flathead screwdriver (if the cap is screwed on), a small brush (like a bottle brush or a pipe cleaner), white vinegar, a clean cloth or sponge, and possibly a pair of pliers (if the cap is stuck). You may also want a small bucket or pan to catch any water that might spill out.

It is a good idea to turn off the power to the dishwasher before cleaning the air gap, especially if you will be removing any hoses. You can also turn off the water supply under the sink to be safe, though it is not strictly necessary for just cleaning the air gap body.

Step-by-step air gap cleaning

Follow these steps to clean your air gap thoroughly:

1. Remove the cap. Depending on your model, the cap may lift straight off, twist off, or require a screwdriver. If it is stuck, try twisting it gently while pulling upward. You can also soak it with hot water or vinegar to loosen any debris.

2. Clean the cap. Once removed, soak the cap in a bowl of vinegar for at least 10 minutes. Then scrub it with the brush to remove any buildup. Rinse it with water and set it aside.

3. Clean the body. Look inside the air gap body. You should see two openings: one that connects to the dishwasher drain and one that goes to the sink drain. Insert the brush into each opening and scrub the inside walls to dislodge any debris. You can also use a small flashlight to see what is inside.

4. Flush the air gap. After scrubbing, run water from the sink faucet into the air gap. This will help rinse away any loose particles. You can also use a spray bottle with water or a vinegar solution to flush from the top.

5. Check the hoses. While the cap is off, inspect the hoses that connect to the air gap underneath the countertop. If you see any kinks or blockages, you may need to clean or replace them. For instructions on cleaning the drain hose, see our dishwasher drain hose cleaning guide.

6. Reassemble. Once the air gap is clean and flushed, replace the cap securely. Turn the dishwasher back on and run a rinse cycle to confirm everything works properly.

How often should you clean the air gap?

A good rule of thumb is to clean the air gap every three to six months, depending on your usage and water hardness. If you run your dishwasher daily and have hard water, you might need to clean it more often, perhaps every two months. If you notice any signs of clogging, clean it right away.

Regular maintenance of the air gap is part of a broader dishwasher care routine. You should also clean the dishwasher filter regularly and check the spray arms for blockages. For more tips, see our dishwasher filter cleaning guide and spray arm cleaning guide.

When cleaning does not restore drainage

If you have cleaned the air gap thoroughly and your dishwasher still does not drain, the problem may be elsewhere. Common culprits include a clogged drain hose, a faulty drain pump, a blocked garbage disposer, or a plumbing issue in the sink drain line.

Start by checking the drain hose for kinks or blockages. You can also remove the hose from the air gap and run water through it to see if it is clogged. If the hose is clear, the issue might be with the drain pump. See our dishwasher drain pump cleaning guide and the dishwasher not draining troubleshooting article.

If you are still stuck, it might be time to call a plumber or appliance repair technician. They can diagnose the issue with specialized tools.

Preventing future clogs

Prevention is always better than cleaning. Here are some habits that will help keep your air gap clear:

Scrape food scraps off dishes before loading, but avoid pre-rinsing everything. As the ENERGY STAR program points out, rinsing dishes before loading increases water and energy use, and modern dishwashers are designed to handle food particles. Simply scraping is enough.

Run your garbage disposer before the dishwasher drains. This helps clear any debris in the sink drain that could back up into the air gap.

Use a dishwasher cleaner or vinegar rinse once a month to break down grease and mineral deposits.

Check the air gap visually every few months. If you see sediment or a slow drain, clean it immediately.

What to pick for your use

Questions

Why is my air gap leaking?

A leak usually means the air gap is clogged. Clean the cap and body. If it still leaks, the hose connection underneath may be loose or the device is cracked. See the cleaning steps above.

Do all dishwashers need an air gap?

Not necessarily. Some dishwashers use a high-loop drain hose instead. Check your local plumbing code to know what is required. The air gap is a common requirement for built-in models.

Can I clean an air gap with bleach?

You can, but white vinegar is usually enough and is less harsh. Avoid abrasive scrubbers that can damage the plastic or metal.

How do I remove a stuck air gap cap?

Try twisting it gently while pulling upward. If it is sealed with mineral deposits, soak it with vinegar and wait a few minutes before trying again.

Should I call a plumber to clean the air gap?

Usually not. Cleaning the air gap is a simple DIY task. If you notice persistent clogs after cleaning, the problem may be elsewhere, and a plumber might be useful.

What if my air gap is completely blocked and water won't drain at all?

If cleaning the cap and body does not clear the blockage, you may need to remove the hoses and clean them separately. Check the drain hose for obstructions and clear them. If the blockage is deep in the plumbing, you may need professional help.

Is it normal for the air gap to make a gurgling sound?

A gurgling sound during draining can indicate a partial clog or improper venting. Clean the air gap and ensure the drain hose is not kinked. If the sound persists, check the sink drain and the dishwasher drain hose for blockages.

How do I know if my dishwasher has an air gap or a high loop?

Look for a small cylinder on the countertop near the sink. If you see one, you have an air gap. If there is no external device, the drain hose may be looped up under the countertop. You can trace the hose to see its path.