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 fixtures that provide backflow prevention device for your dishwasher. But, what does air gap plumbing do, exactly? A properly maintained and installed air gap prevents drain water backing up into the dishwashing machine and the result of possible contamination.

The plumbing code 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.

The air gap is the cylinder-like vent fixture located next to the sink faucet that permits air admittance to the drain piping and plumbing system below the sink and countertop. The drain pipe, or drain hose, 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 trap or into the garbage disposal. If at any time, water flows from the plumbing systems fixture into the sink, the pipe and plumbing may be backed up and clogged, and it might be time to call out your local San Diego plumbers for maintenance or repair of your backflow preventer.

If you are thinking about installing a new dishwasher, and do not have an air gap, or are having issues with your current dishwashing setup, 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).