Why Your Dishwasher Needs a High-Loop Drain (And How to Check If It’s Installed Correctly)

A seemingly small detail in your kitchen plumbing—your dishwasher’s high-loop drain—is critical in keeping your home safe from contamination and costly plumbing issues. In fact, the North Carolina Residential Code (NCRC) mandates its installation to maintain proper backflow prevention and sanitation standards.

Let’s explore why this detail is essential, how it keeps your dishwasher running efficiently, and how to check if yours is installed correctly.

What Is a High-Loop Drain?

A high-loop drain involves routing the dishwasher’s drain hose to rise as high as possible under the kitchen sink—typically secured to the underside of the countertop—before descending to the drain or garbage disposal. This creates a “high loop” that prevents wastewater from your sink or garbage disposal from siphoning into the dishwasher.

Without a high-loop installation, you risk cross-contamination from dirty water backing into your dishwasher, resulting in foul odors, harmful bacteria growth, and potential appliance failure.

The Code Requirement: North Carolina Residential Code

The NCRC, like other state codes, emphasizes backflow prevention in household plumbing. The code mandates that dishwashers be equipped with either a high-loop drain or an air gap device to protect the appliance from contamination via backflow.

A high-loop configuration is often used in residential settings because it is easy to install, inexpensive, and doesn’t require additional hardware like an air gap. While both methods are code-compliant, proper installation is critical to meeting code standards and avoiding plumbing issues.
 

How to Check If Your High-Loop Drain Is Correctly Installed

It’s easy for homeowners to inspect their dishwasher setup to confirm proper installation. Here’s how to check:

1. Locate the Dishwasher Drain Hose:

Open the cabinets under your sink and look for the drain hose coming from the dishwasher.

2. Check for Elevation:

Confirm that the hose rises to the highest point possible—near the bottom of the countertop—before descending to the garbage disposal or drain.

3. Look for Secure Fastening:

The high loop should be secured with a bracket or clip to prevent it from sagging. A loose hose can cause the loop to flatten, defeating its purpose.

4. Inspect Connections:

Ensure the hose is firmly connected at both ends (dishwasher outlet and garbage disposal/drain inlet). Look for any signs of leaks or wear along the hose.

If your dishwasher’s hose is sagging or doesn’t rise high enough, you can secure it to the underside of the counter with a simple clamp or zip tie.

Final Thoughts

Ensuring your dishwasher’s drain is appropriately installed keeps your kitchen sanitary and helps you avoid costly plumbing repairs. A high-loop drain isn’t just a suggestion—it’s a necessity outlined in building codes to keep your home safe and efficient.

Next time you load the dishwasher, take a moment to check that your drain hose is installed correctly. Minor fixes like this one can make a big difference!
 
With this easy inspection tip, homeowners and real estate agents can confidently avoid plumbing headaches and ensure code compliance for every kitchen.
 
Would you like to explore other ways to enhance your home’s plumbing or prepare for your next inspection? Contact Anchor & Crow Home Inspections for expert guidance and a comprehensive home evaluation!