Modern dishwashers are required to have an air gap or an equivalent backflow prevention device to protect a home’s water supply from contamination. When a kitchen sink is installed without an air gap, there is a risk that dirty water from the sink or dishwasher drain could siphon back into the dishwasher, potentially contaminating clean dishes or even the home’s potable water system.
What Is an Air Gap?
An air gap is a small fitting, typically mounted on the sink deck or countertop, that provides a physical separation between the dishwasher drain line and the household plumbing system.
It prevents dirty water from flowing backward by ensuring there is always an open space (air) between the two systems.
Many building codes require it as the primary method of dishwasher backflow protection.
Why the Lack of an Air Gap Is a Concern
Backflow Risk: Without an air gap, wastewater can be siphoned back into the dishwasher during drainage, especially if the sink drain becomes clogged.
Health Hazard: Contaminated water can leave bacteria or food waste inside the dishwasher, affecting sanitation.
Code Compliance: In many jurisdictions, a missing air gap means the installation is not up to current plumbing code.
Inspection Limitation: Some homeowners or installers rely on alternative devices (like high-loop installations or check valves), but these may not provide the same level of protection as a true air gap.
Recommended Actions
Install a Code-Compliant Air Gap
Have a licensed plumber install a proper air gap fitting on the sink deck or countertop.
Alternative Solutions
In some jurisdictions, a “high loop” in the dishwasher drain line (looped up and secured under the countertop) is allowed, though this is less reliable.
Some dishwashers have built-in check valves, but these should be verified for local code acceptance.
Regular Maintenance
Keep the air gap clean by occasionally flushing it with water and checking for blockages.
Conclusion
A kitchen sink without an air gap is a plumbing oversight that can create sanitation risks and code compliance issues. Installing a proper air gap is typically inexpensive and provides lasting protection against wastewater backflow, ensuring both health safety and system reliability.