What Is a Dishwasher Air Gap?

By Toni Matthews-El

A dishwasher air gap is a small, egg-sized item that connects your dishwasher to the kitchen sink drain. It’s usually mounted above the sink near your faucet. This device can prevent contaminated water from draining back into the dishwasher. From a practical standpoint, they’re important devices. After all, who wants their clean dishes getting coated in the grime that was just washed away?

If you’re not required by a local or state ordinance to have an air gap, you might not appreciate how crucial this device is for keeping your kitchen water sanitary. In this article, you’ll learn why an air gap is important, where it should be located if you’re required to have one, and how to clean the device if the need arises.

Why is a dishwasher air gap important?

The main purpose of a dishwasher air gap is to prevent wastewater from leaking into your clean water supply. Even if some consider them an eyesore, there’s no arguing against their practical importance.

It’s common for a high loop to get used as an alternative to an air gap. However, some plumbing codes require dishwasher air gaps because they’re the one approach guaranteed to effectively separate clean and contaminated water.

Standards and codes related to dishwasher air gaps

Dishwasher air gap codes vary from building to building, town to town, and state to state. The best thing you can do is check into whether you must have a dishwasher air gap. Ordinances and codes are often published online on your local government website.

Local or state websites usually provide a contact number, so consider calling to ask if there are any plumbing codes in your area that make air gaps a must. If you’re renting a home, ask your landlord if these devices are required.

Certain states, such as Minnesota, do require a dishwasher air gap. As of 2016, Minnesota’s code reads as follows:

No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher air gap fitting on the discharge side of the dishwashing machine. Listed air gaps shall be installed with the flood-level (FL) marking at or above the flood level of the sink or drainboard, whichever is higher.

If you want your dishwasher air gap professionally installed, work with plumbing inspectors that are familiar with the process and understand the most up-to-date standards or codes for these items.

How a dishwasher air gap works

The dishwasher air gap keeps dirty drain water away from your clean water supply. Air gaps have two hoses: an “in” hose on the right side where water gets forced upward by the dishwasher pump and an “out” hose that drains water using gravity. Some dishwasher units automatically come with an air gap but not all do.

For a dishwasher air gap to work efficiently, the “out” hose should always be larger than the “in” hose. Otherwise, it could lead to drainage issues.

Troubleshooting air gap problems

There are a few issues that might arise with your dishwasher or air gap. Here are the most common:

An improper hose size exists

As mentioned, an “out” hose that’s too small can cause drainage issues. That’s because it won’t be big enough to properly handle the water flow when it’s not under pressure. This will cause water to discharge out of the dishwasher air gap, which should not happen. To avoid this, make sure that the “out” hose is larger than the “in” hose.

The knockout plug wasn’t removed

It’s possible that when your dishwasher or garbage disposal unit was newly installed, the installer might have forgotten to remove the knockout plug. Unless this plug gets removed, your dishwasher won’t drain properly.

To fix this, use a hammer and screwdriver to tap the knockout plug that’s causing the issue. Then, reconnect the drain hose to the disposal unit. After that, unplug the garbage disposal and reach in to remove the knockout plug. 

Your dishwasher air gap is clogged

If water is gushing out of the air gap, this is usually a sign that it’s blocked. Check for food particles or other objects that could be keeping your dishwasher from draining properly.

A leak is present

There may be tiny holes in the drain hose that are causing drainage issues. Identify the holes using a permanent marker. Next, spread epoxy putty over the holes, making sure the putty covers an area of at least a one-inch margin. Lastly, give the putty a full 24-hours to dry. This approach should fix holes and prevent future leaks.

How to clean your dishwasher air gap

To keep your dishwasher air gap in good condition, consider cleaning it every couple of weeks.

Materials

  • Screwdriver
  • Sponge
  • Homemade cleaning solution
  • Toothbrush
  1. Remove your air gap. To do this, take off the chrome cap cover and unscrew the plastic cap.
  2. Have someone hold the air gap device in place while you remove the bolts.
  3. Once the bolts are unscrewed, remove the drain lines from the dishwasher and garbage disposal.
  4. Dab a little cleaning solution on a sponge and wipe around the inside of the device, removing any dirt or food particles.
  5. If you find that there are stains or debris that are difficult to remove, try scrubbing them away with a toothbrush. Be careful not to scrub so hard that you damage the device. 
  6. Flush the holes connecting the hoses with water.
  7. Straighten out the air gap device ensure that it’s draining properly.

How to reinstall your dishwasher air gap

Before reinstalling your dishwasher air gap, replace the washers you removed before taking the device out to clean it. Once your washers are exchanged for new ones, place your drain hoses back into their original positions and tighten the clamps. Again, consider having someone else help you hold parts in place during this process.


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