What is an Air Gap, Exactly?

What is an Air Gap, Exactly?

According to the Wikipedia, an air gap is an “unobstructed vertical space between the water outlet and the flood level of a fixture.” What does that even mean? And, did you know that having an air gap installed with any dishwasher is now required by Uniform Plumbing Code?

The most common use of the term “air gap” refers to the plumbing fixture that provides back flow prevention for your dishwasher. But, what does it do, exactly? A properly maintained and installed air gap prevents drain water backing up into the dishwasher and causing possible contamination.

The code for plumbing in San Diego requires all dishwashers be installed with an air gap because of the possible contamination factor. Although it is a small chance, the possibility for dirty water to be siphoned into the dishwasher drain line and then into the main water supply line is still a possibility and an air gap will prevent this. Some people might advise that you can go with a “High Loop” method of bringing the dishwasher drain up to the highest point under the sink before connecting to the sink drain. However, in San Diego, plumbers (licensed and by the book) and appliance installation crews will not install or hook up a dishwasher using this method, nor will it pass inspection from the city. It is best to follow all safety codes.

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The air gap is the cylinder like fixture located next to the sink faucet.The drain pipe of the dishwasher feeds to the top of the air gap, and the bottom of the air gap is plumbed into the sink drain below the basket or into the garbage disposal. If at any time, water flows from the fixture into the sink, it might be time to call out your local San Diego plumbers for maintenance or repair.

If you are thinking about installing a new dishwasher, and do not have an air gap, call Bill Howe Plumbing in San Diego for a free estimate. You’ll save time and be fully prepared when your new dishwasher arrives! Call 1-800 Bill Howe (245-5469).


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