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What is a dishwasher air gap?

A dishwasher air gap is a cylinder fitting that connects the kitchen sink drain to your dishwasher, preventing dirty water from flowing into the dishwasher as well as out of it during a wash cycle. Whirlpool® dishwashers have several important features that keep dishes clean, including the small yet effective dishwasher air gap.

Because your dishwasher drains directly into your kitchen plumbing, the dishwasher air gap stops any dirty dishwater from re-entering the appliance. Read on to learn more about dishwasher air gaps and how they work:

A kitchen sink with an air gap displayed A kitchen sink with an air gap displayed

How does a dishwasher air gap work?

Dishwasher air gaps work by separating two branches of hose with an unpressurized gap of air to prevent cross-contamination between the dishwasher and drain. While one branch of the air gap fitting connects to the appliance, the other connects and descends to the garbage disposal. Dirty dish water is pumped out of the appliance and into the air gap through the hose, where it is then released to the drainage site through the second branch of tubing.  

Is an air gap necessary for a dishwasher?

Air gaps function on the principle of basic physics. Because it’s impossible for water to flow back through an unpressurized gap of air, they prevent water from being siphoned out while the dishwasher is in use and keep dirty, used water from re-entering the unit. While there are some alternatives to keeping your dishwasher water flowing in the right direction, like using a high loop or standpipe, air gaps can prevent siphoning or backflow in any given circumstance and have been mandated by building codes in several states.

Air gaps can also prevent sink water from being forced into the dishwasher in the event that the drain or garbage disposer becomes clogged. Most dishwashers also incorporate check valves in the drain system to prevent this from happening. For additional protection, the drain hose can be routed to the underside of the counter to negate gravity from allowing sink water into the unit should the check valve fail.

Two extended dishwasher racks filled with dishes Two extended dishwasher racks filled with dishes

Do new dishwashers need an air gap?

A dishwasher air gap’s purpose is to help ensure that the water being used in your appliance is fresh and isn’t siphoned out early during a wash cycle. If you live in a state where air gaps are mandated by law, even a new dishwasher will require one to be installed. A drain hose that is connected to house plumbing lower than 20 inches above the floor will need an air gap. Check your local codes and requirements.

Unless mandated, dishwasher air gaps are not always recommended by professionals. Dirty water can also be prevented from entering your dishwasher by routing the drain hose beneath the counter at the same height as a full sink of water. This allows the high loop to counteract the gravity from letting water from the sink get into the dishwasher. Some Whirlpool® dishwashers are designed with built-in air gaps on the drain end. However, these devices are not recognized by code agencies and will not prevent the use of a through-counter device where required by code.

An internal image of wash action inside a dishwasher An internal image of wash action inside a dishwasher

Should water come out of the dishwasher air gap?

If your dishwasher air gap is leaking water, this indicates a problem that will need to be corrected. Water spilling from an air gap is typically caused by a clog that can oftentimes be cleared out by trying a few simple methods on your own.

How do I clear my dishwasher air gap?

To clear a clog from your dishwasher air gap, remove the cover and use a long-handled bottle brush to remove food particles that may be stuck in the tubing. You can also try clearing the clog by placing a paper towel tube over the opening and blowing into it to dislodge the debris. 

If neither of these methods work and your garbage disposal was recently installed, it’s possible that the knockout plug was never removed. To remove the knockout plug, unplug the disposal and disconnect the hose linking the air gap drain to it. Use a hammer and screwdriver to tap the knockout plug out of place to allow water to flow through the tubing. Once you have reconnected the drain hose, reach inside the disposal to remove the loose plug before plugging it back into the power supply.

If none of these techniques work and the air gap is still leaking, it may be time to contact a professional. Repair and replace services from Whirlpool brand provide professional help when you need it.

Shop Whirlpool® dishwashers

If you’re ready to purchase a Whirlpool® dishwasher, you can choose from several efficient and long-lasting options.

 Learn More about Whirlpool® Dishwashers

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