A dishwasher air gap is part of the necessary plumbing required when installing a dishwasher. Local plumbing code typically requires an air gap to ensure sewage backup does not contaminate your dishwasher. But what is a dishwasher air gap, and why is it so important?

What is a Dishwasher Air Gap?

The dishwasher air gap is critical because it prevents sewage from flowing back into the dishwasher. If your sewage line backs up, the water will drain up through the air gap into your sink rather than back into your dishwasher. Air gaps for dishwashers are the most effective anti-backflow devices and should not be substituted with another method.

How Does a Dishwasher Air Gap Work?

The air gap consists of two drain hoses. One is expelling waste water from the dishwasher, and the other is leading the wastewater to the garbage disposal. An air gap separates the two drain hoses to prevent the wastewater from backing up and contaminating your dishes.

No water or air should be expelled from the dishwasher air gap. But if there is, there’s a possibility that it may be improperly installed or clogged with debris.

Where is it Located?

The air gap for dishwashers is typically located in parallel with the sink faucet. Usually, it will be covered by a chrome cylinder. It’s important that the chrome cylinder is installed and the three slats are pointing toward the sink (so the water flows into your sink, not behind it!).

What Kind of Problems Can a Dishwasher Air Gap Experience?

Sometimes, water can flow out of the air gap. A damaged seal or a blockage in the pipe can be responsible for this. Other potential problems include a clogged air gap and a clogged vent. If you think that your air gap is clogged, check out this video that shows you how to clean your dishwasher air gap.

Improper Installation

To see if water or air leakage is due to improper installation, check under your sink to see the sizes of your drain hoses. The “out” hose (heading to the garbage disposal) should be bigger than the “in” hose. The air gap system won’t work correctly if they are the same size.

Another possibility is that the knockout plug wasn’t removed upon installation, preventing the water from flowing into the “out” drain hose. This is more likely if it was recently installed, and the installer may have forgotten to take it out. The drain hose leading to the garbage disposal must be disconnected and tapped out to allow the water to flow freely to remove the knockout plug.

Clogged Air Gap

If improper installation has been ruled out, debris is likely causing an obstruction. There are a couple of different methods that can help.

First, remove the air gap cover and get an empty paper towel roll. Place the paper towel tube over the hose openings and blow into the gap. This can help dislodge the food particles.

If that doesn’t work, you can also try dislodging the food particles with a long-handled bottle brush. Worst-case scenario, you may have to call a plumber to help you snake out the drain lines.

Can I Use Different Anti-Backflow Devices?

Check valves are sometimes used as an alternative to an air gap, but experts consider them less efficient since they tend to malfunction if food gets stuck in the valve.

Alternatively, handymen may recommend installing the drain hose using the high loop method. Although this method will prevent sewage from siphoning into your dishwasher under low-pressure backups, it will not prevent an overflow if the backup is high pressure or high sewage. For this reason, this method is not typically recommended.

If you’re installing a new dishwasher or received a warning from an inspector that an air gap is required on your current dishwasher, your best bet is to contact a plumber or appliance technician to install the air gap.

If you live in the Tampa Bay area and want to install it yourself, Appliance & A/C Parts Today can help! We have all the parts you’ll need and offer free technical advice. Contact us today!