How To Plumb A Double Sink With Dishwasher: Step-by-Step Guide (2025)

Why This Matters: You’re Not Just Installing Pipes—You’re Building a Smarter Kitchen

Imagine this: You just bought a beautiful new double sink, paired with a sleek dishwasher. But when you turn on the water, it gurgles… then leaks. Or worse—the dishwasher won’t drain, and your kitchen floor is a puddle.

You didn’t sign up for this.

If you’re wondering how to plumb a double sink with dishwasher, you’re not alone. Thousands of DIYers face this exact challenge every year. The good news? With the right steps, you can do it safely, correctly, and without calling a plumber—saving hundreds of dollars.

This guide walks you through exactly how to connect your dishwasher to a double sink drain system—using clear, proven methods trusted by licensed plumbers and home improvement experts. No jargon. No guesswork. Just results.

Can You Connect a Dishwasher to a Double Sink? (Yes—Here’s How)

Absolutely. In fact, over 78% of modern kitchens with double sinks include a dishwasher connection (Source: National Association of Home Builders, 2024). The key is understanding how the drainage system works.

A double sink typically has two basins connected to a single drain pipe via a double bowl strainer assembly. Your dishwasher needs to tap into this system—without creating a vacuum, backflow, or clog.

The magic happens at the air gap or high-loop drain hose, which prevents dirty sink water from flowing back into your clean dishes. This isn’t optional—it’s required by plumbing code in most U.S. states.

“A properly connected dishwasher drain is critical to prevent contamination. Never drain directly into the garbage disposal or sink trap without an air gap or high loop.”
— Plumbing Code Handbook, International Residential Code (IRC) Section P2703.3

What Tools & Materials Do You Need?

Before you start, gather these essentials:

💡 Pro Tip: Buy a dishwasher with a built-in air gap if your local code allows it. It’s easier than installing a separate air gap on the countertop.

Step-by-Step: How To Plumb A Double Sink With Dishwasher

Follow these 7 simple steps. We’ll walk you through both the garbage disposal method (most common) and the tailpiece method (for sinks without disposals).

Step 1: Turn Off Water & Power

• Shut off the water supply under the sink.
• Turn off the circuit breaker for your dishwasher (if already wired).
• Place a bucket under the P-trap to catch residual water.

Step 2: Remove the Existing Drain Assembly

• Unscrew the slip nuts connecting the sink strainers to the tailpiece.
• Remove the old strainers and clean the sink openings.
• If you have a garbage disposal, disconnect it temporarily (you’ll reconnect it next).

Step 3: Install the Double Bowl Strainer Kit

• Apply plumber’s putty or silicone around the flange of each strainer.
• Insert each strainer into its basin and tighten the mounting nut from below.
• Reconnect the two basins using a Y-fitting or double bowl tailpiece.

✅ Critical Detail: The tailpiece must slope downward at least 1/4 inch per foot to ensure proper drainage. Use a level to check.

Step 4: Connect the Dishwasher Drain Hose

Now, the crucial part.

Option A: Connecting to a Garbage Disposal (Recommended)

• Most double sinks have a disposal on one side. This is ideal.
• Locate the dishwasher inlet port on the side of the disposal (usually a ⅝” knockout plug).
• Remove the plug with a screwdriver and hammer.
• Insert the dishwasher drain hose into the port.
• Secure with the provided hose clamp—tighten until snug, but don’t crush the hose.

Option B: Connecting to the Tailpiece (No Disposal)

• If you don’t have a disposal, you’ll attach the hose to the tailpiece under the sink.
• Use a drain saddle clamp (available at hardware stores) to pierce the tailpiece.
• Insert the hose into the saddle and tighten the clamp.
• Important: The hose must rise to form a high loop—at least 20 inches above the floor—before connecting to the sink drain. This prevents backflow.

📌 Did You Know? The high loop is required by the International Plumbing Code (IPC) to prevent sewage from siphoning back into your dishwasher. Skipping this can cause serious contamination. Learn more about plumbing codes on Wikipedia .

Step 5: Route the Hose Properly

• Run the hose from the dishwasher to the sink area.
• Avoid kinks or sharp bends—these cause clogs.
• Use zip ties to secure the hose to the cabinet wall or underside of the counter.
• Ensure the high loop (if no disposal) is secured above the sink’s flood rim.

Step 6: Reconnect & Test

• Reattach the P-trap and slip nuts under the sink.
• Turn water back on.
• Run the dishwasher on a short cycle (e.g., “Rinse Only”).
• Watch for leaks at every connection point.
• Check under the sink for drips for at least 10 minutes.

Step 7: Install the Air Gap (If Required)

• Some areas require a visible air gap on the countertop (looks like a small chrome cap).
• If yours does, connect the hose from the dishwasher to the air gap inlet, then run a second hose from the air gap to the drain tailpiece.
• Note: Many new dishwashers now have “built-in air gaps” that meet code without the countertop fitting. Check your manual.

High Loop vs. Air Gap: Which Should You Use?

👉 Recommendation: Use a high loop if your local code allows it. It’s simpler, cheaper, and just as effective. If you’re in California, New York, or Massachusetts, you’ll likely need the air gap.

Common Mistakes to Avoid

Don’t fall into these traps—most DIY disasters come from these 3 errors:

1. Skipping the high loop or air gap → Risk of dirty water backflow into dishes.
2. Using a hose that’s too long or coiled → Creates siphoning and slow drainage.
3. Overtightening slip nuts → Cracks PVC or brass fittings. Hand-tight + ¼ turn with wrench is enough.

🛑 Real Case: In 2023, a homeowner in Ohio skipped the air gap. After 3 months, his dishwasher filled with soapy sink water. Repairs cost $850. A $15 air gap would’ve prevented it.

FAQ: Your Top Questions About Plumbing a Double Sink With Dishwasher

Q1: Can I connect a dishwasher to a double sink without a garbage disposal?

Yes. You’ll connect the dishwasher drain hose to the tailpiece using a saddle clamp and create a high loop (minimum 20 inches above floor). This meets plumbing code and prevents backflow. Just ensure the hose rises higher than the sink’s flood rim before connecting.

Q2: Do I need an air gap for my dishwasher?

It depends on your location. Most U.S. states require an air gap unless your dishwasher has a built-in anti-siphon device approved by the manufacturer. Check your local plumbing code or ask your city’s building department. If unsure, install one—it’s cheap insurance.

Q3: Why is my dishwasher draining slowly after installation?

Likely causes:

• Kinked or crushed drain hose
• High loop too low (<20 inches)
• Clogged air gap (clean it with a toothbrush)
• Improper slope of tailpiece (must fall 1/4″ per foot)

Run hot water through the sink first, then run a short dishwasher cycle. If still slow, inspect all connections.

Q4: What’s the best way to seal the sink strainers?

Use plumber’s putty for metal strainers or silicone sealant for acrylic or composite sinks. Apply a thin rope around the flange before inserting. Wipe away excess with a damp cloth. Never use Teflon tape—it’s for threaded pipes, not sink drains.

Q5: Can I use a garbage disposal with a double sink?

Yes—and it’s the preferred method. Install the disposal on the side you use most (usually the right side). Connect the dishwasher to the disposal’s inlet port. The disposal helps grind food particles before they enter the drain line, reducing clogs.

Q6: How long does this project take?

For a first-timer: 2–3 hours. With experience: under 90 minutes. Plan for extra time if you’re replacing old pipes or dealing with rusted fittings.

Final Thoughts: You’ve Got This

Installing a dishwasher with a double sink isn’t magic—it’s method. By following these steps, you’ve not only saved money—you’ve built a safer, more efficient kitchen that works the way it should.

You now understand:

• Why the high loop or air gap is non-negotiable
• How to connect to either a garbage disposal or tailpiece
• How to avoid the mistakes that cost others hundreds

And best of all? You did it yourself.

If this guide helped you, share it with a friend who’s tackling a kitchen remodel.
👉 Tag them on Pinterest or Facebook: “Just fixed my dishwasher drain—here’s how!”

And if you’re planning your next upgrade, check out our guide on How to Choose the Best Kitchen Sink Material (coming soon!).