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Dishwasher Air Gap | Is It Required in California?

Air gaps are actually an essential piece of equipment when it comes to dishwashers, despite the fact that your average non-DIYer may have no inkling as to what they are or what they do.

This little cylinder is the make or break for water supply protection when it comes to dishwashing appliances and is regulated by the building and plumbing codes for many states.

Air gaps are required for all dishwashers in the state of California, according to the California Plumbing code. These air pressure-based fittings are essential for keeping sewage out of dishwashers without risk of failure, provided they are approved and listed.

California Codes Require Dishwasher Air Gaps

Air gaps are required in California according to Section 807.3 of the California Plumbing Code, which states that:

“No domestic dish washing 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.”

Why Are Air Gaps Necessary?

Like a backdraft damper, an air gap works to keep things separate. It is not merely a gap but a tube that connects to the dishwasher and the drain, and it is designed to prevent the backflow of dirty water.


A more comparable example is how a clogged sink drain will flow up into the sink, but won’t reach your faucet, keeping your water supply clean.

So, an unpressurized cylinder separates the branch of the hose that leads to the dishwasher and the one that leads down to the disposal.

Water leaves the appliance and enters the air gap first, and from there, it then drains into the second stage toward the waste drain.  

Without pressurized air in that tube, water cannot be pulled out while the dishwasher is in use, and the sewage water doesn’t go back into the appliance.

It also acts as a fail-safe for dishwashers’ innate check valve (which can fail) if your garbage disposal gets blocked up. I wouldn’t like to open my dishwasher to find my clean plates sitting in grey and brown drain water!

This air gap has a head that protrudes up by your sink. It has a hole for air and will also expel built-up water instead of letting it go through your dishwasher.

For more information, you can check out Dishwasher Air Gap: What It Is and Why Is It Used?

Dishwasher Air Gap Requirements

There are requirements for what air gap you can use. These devices must be listed and approved by the International Code Council (ICC).

A listed item has been assigned a listing code that comes from an ICC-approved organization that tests and regulates safety and performance. The International Residential Code (IRC), per Section P2717.1, requires an air gap to have an ASME A112.1.3/A112.1.2 listing.

An air gap must comply with ASME A112.1.2, while a fitting version must have an ASME A112.1.3 listing (Section P2902.3.1).

ASME is the American Society of Mechanical Engineers. When a product is ASME accredited, this means that it complies with regulations in the codes and attests to the quality and safety of the product.

To say that your air gap must be approved means that the IRC agrees with the testing and standards of the organization (for which it provides a rating), and that by using an appropriately listed item, you are complying with code regulations.

Code Installation Requirements

The IRC, Section P2902.3.1, measures air gaps vertically between the lowest part of the water outlet and the flood level rim. This dimension must be double the diameter of the effective opening.

If you look at the California code quoted earlier in the article, you can see that an air gap must be installed on par with or above the sink or draining board level. This relates to the flood level.

Stainless steel faucet with dishwasher air gap installed

An air gap has a literal opening in it to add air into the system and prevent pressure from building in the tube. You need to install this at or above the sink line or drainage board in order to prevent any backed-up water from overflowing into your cabinets, damaging them and your flooring.

By installing the air gap above the dishwasher, you keep siphoning from occurring and allow any overflowing drain water to eject into the sink where it can drain away.

Do All Dishwashers Require Air Gaps?

All dishwashers, even new ones, are required by law in California to have an air gap.

Other methods (high loop and standpipe) serve a similar function to an air gap. Still, the air gap fitting is the most reliable way to protect your water supply and is, therefore, adopted as the regulated method in many states.

Most dishwashers do not have an in-built air gap (only a check valve), so you will likely need to purchase and install the device. This is probably because not all states require them. Even the IRC does not specify their inclusion in the dishwasher drainage system. California has added this regulation.

You might come across sources that tell you it is possible to bypass the air gap requirement by performing the installation yourself or even by removing the air gap after inspections are complete.

But this would compromise your insurance and warranty claims, and the latter would render your claims fraudulent.

Even if your state doesn’t require an air gap to prevent backflow, I still recommend an air gap over alternatives.

It is the most highly-rated way to prevent sewage water from entering your dishwasher and flooding out of clogged drainpipes since there are no moving parts that can break and cause the device to fail.

There are also many aesthetic ways to incorporate the air gap into your kitchen, which makes the protrusion a worthwhile feature to deal with.

KRAUS Dishwasher Air Gap in Spot Free All-Brite™ Stainless Steel, KAG-1SFS
  • CLEAN HOME PRODUCT prevents wastewater from backing up into your dishwasher, eliminating the risk of contaminating your clean dishes – OVERALL HEIGHT with plastic body: 9 in. – CAP HEIGHT: 2 1/2...
  • AIR GAP KIT includes durable ABS plastic body and solid brass cover for a lifetime of reliable performance – SOLID BRASS COVER offers superior durability and a high-end appearance
  • CODE COMPLIANCE: Air gaps are required for dishwasher installations by plumbing codes in many states – 1 YEAR WARRANTY: Satisfaction guaranteed with best-in-industry customer support that puts you...
  • CORROSION AND RUST-RESISTANT FINISH: Premium corrosion-resistant finish will not dull or fade over time, comes in a range of colors to complement your kitchen faucet – UNIVERSAL DESIGN compatible...
KOHLER K-9110-BN Air Gap Body with Cover, Vibrant Brushed Nickel
  • Brass air gap completely covers clamping collar
  • 5/8 inch dishwasher inlet
  • 7/8-inch outlet to disposal or sink
  • Complements KOHLER faucet finishes

Last update on 2024-05-29 / Affiliate links / Images from Amazon Product Advertising API


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