What Are Dishwasher Air Gaps and Are They Necessary?


When installing or updating a kitchen, few components are as misunderstood yet essential as the humble dishwasher air gap. This small device plays a crucial role in keeping your dishwasher and water supply safe from contamination. But what exactly is a dishwasher air gap, and do you really need one? This guide will explore everything you need to know about dishwasher air gaps, from their function and installation to troubleshooting common problems.

Understanding Dishwasher Air Gaps

Definition and Functionality

A dishwasher air gap is a simple device that prevents contaminated water from backing up into your dishwasher and potentially entering your clean water supply. It typically appears as a small, cylindrical fixture mounted on the countertop near the sink or can be hidden underneath. The air gap works by allowing air into the dishwasher’s drain hose, which prevents any dirty water from siphoning back into the dishwasher or your clean dishes.

Do You Need an Air Gap?

Depending on where you live, a dishwasher air gap might be more than just a recommendation—it could be a legal requirement. Many states in the U.S. require air gaps as part of residential plumbing codes. However, if you are in a region where they are not mandated, or if an air gap installation isn’t feasible due to space or other constraints, alternatives like high loops (routing the hose in an upward arc) might be acceptable. Still, these alternatives may not offer the same level of protection against backflow.

Installation and Requirements

Installation Guide

Installing a dishwasher air gap is a task most homeowners can handle. Here’s a simplified step-by-step process:

  1. Locate the mounting hole on your sink or countertop. If there isn’t one, you might need to drill a new hole.
  2. Insert the air gap through the hole and secure it with the mounting nuts provided.
  3. Connect the hoses: One hose runs from the dishwasher to the air gap, and another from the air gap to the garbage disposal or drain.
  4. Check for leaks by running the dishwasher and observing any leakage around the air gap.

Common Mistakes to Avoid

  • Not tightening connections sufficiently, leading to leaks.
  • Incorrect hose lengths that lead to kinks or loops, which can impede function.

Troubleshooting Common Issues

Common Problems and Solutions

If your air gap starts leaking, or if water is backing up into your sink, it’s usually due to clogs formed by debris and food particles. To fix this:

  • Remove the cover of the air gap.
  • Clean out any debris inside with a small brush.
  • Check the hoses for clogs and clear them.

Pros and Cons of Having a Dishwasher Air Gap


  • Prevents contamination of your clean water supply.
  • Compliance with local regulations, avoiding potential legal issues.


  • Aesthetic concerns: Some homeowners find them unsightly.
  • Maintenance: They can clog and require periodic cleaning.

Expert Opinions on Dishwasher Air Gaps

Insights from Professionals

Plumbers and appliance installation experts often emphasize the necessity of having an air gap despite its potential drawbacks. They highlight the peace of mind that comes from knowing your dishwasher and water system are safeguarded against backflow contamination.

Homeowner Experiences

Many homeowners report that after installing an air gap, issues with water backing up into the dishwasher were resolved, showcasing the practical benefits of this small device.


Understanding the function and importance of dishwasher air gaps is crucial for anyone looking to maintain a safe and efficient kitchen plumbing system. Whether mandated by law or chosen for peace of mind, ensuring your dishwasher is equipped with an air gap or a suitable alternative can save you from potential health hazards and costly repairs. Always consult with a professional plumber if you are unsure about the installation or compliance with local codes.

FAQ Section

  • Q: Can I install an air gap myself?
    • A: Yes, with basic DIY skills, you can install an air gap. Follow the guide above for detailed steps.
  • Q: What if my air gap keeps clogging?
    • A: Regular maintenance and cleaning are recommended. If clogging persists, check the installation for any issues with hose routing or length.