So, you’ve decided to remove your garbage disposal—and now you’re staring at a gaping hole under your double sink, wondering what comes next. You’re not alone. Many homeowners choose to ditch the disposal for space, noise, or maintenance reasons—but reconfiguring the plumbing can feel overwhelming. Don’t worry! This guide walks you through how to plumb a double sink after removing garbage disposal safely, efficiently, and in compliance with modern plumbing codes. Whether you’re a weekend warrior or just curious, we’ve got you covered.
Why Does Plumbing Change When You Remove a Garbage Disposal?
Garbage disposals aren’t just appliances—they’re integral parts of your sink’s drainage system. Most are installed on one side of a double sink (usually the left), and their outlet connects directly to the main drain line. When removed, you lose that direct path, which means both sink basins must now share a single, properly vented P-trap system.
According to the International Residential Code (IRC), every fixture must have a trap and proper venting to prevent sewer gases from entering your home. Without correct re-plumbing, you risk slow drainage, gurgling noises, or even health hazards.
💡 Pro Tip: The Uniform Plumbing Code (UPC) and IRC generally allow two sinks to share one trap—as long as they’re within 30 inches of each other and connected via a continuous waste arm. Source: Wikipedia – Plumbing Drain-Waste-Vent System
Tools & Materials You’ll Need
Before you start, gather these essentials:
- Adjustable wrench or basin wrench
- Pipe cutter or hacksaw
- PVC or ABS pipes and fittings (1½” diameter standard for sinks)
- Slip-joint nuts and washers
- Teflon tape or pipe thread sealant
- Bucket and towels (for residual water)
- Plumber’s putty (if reinstalling strainers)
- Measuring tape
Note: Always check local building codes—some municipalities require specific materials or permit inspections.
Step-by-Step Guide: How to Plumb a Double Sink After Removing Garbage Disposal
Step 1: Turn Off Water & Disconnect Old Plumbing
- Shut off hot and cold water supply valves under the sink.
- Place a bucket underneath to catch drips.
- Disconnect the dishwasher drain hose (if present) and any remaining disposal connections.
- Remove the disposal unit and detach the old drain flange from the sink basket.
⚠️ Safety First: Wear gloves and eye protection. Old pipes may contain sharp edges or debris.
Step 2: Install New Sink Strainers on Both Basins
- Clean the sink openings thoroughly.
- Apply plumber’s putty around the underside of each new strainer.
- Insert strainers from above, then secure with locknuts from below.
- Wipe away excess putty.
Standard strainer size: 3½” diameter. Ensure compatibility with your sink.
Step 3: Connect the Two Sinks with a Continuous Waste Kit
This is the heart of the project. You’ll use a continuous waste assembly to link both basins to a single P-trap.
- Attach a tailpiece (straight pipe) to the bottom of each sink strainer.
- On the side where the disposal was (usually left), install a wye fitting or cross tee instead of a standard tailpiece.
- Connect the right-side tailpiece to the side inlet of the wye using a slip-joint extension tube.
- Ensure the horizontal run slopes downward at ¼ inch per foot toward the main drain.
📏 Measurement Matters: Keep the distance between the two sinks’ centers ≤ 30 inches. Longer spans may require a second trap—check local code.
Step 4: Install the P-Trap and Connect to Main Drain
- Attach a P-trap to the bottom outlet of the wye fitting.
- Connect the P-trap’s outlet to the existing wall drainpipe using a slip-joint nut.
- Hand-tighten all connections, then give a quarter-turn with a wrench—do not overtighten, or you’ll crack the fittings.
✅ Test for Leaks: Turn water back on, run both faucets, and check every joint. Minor drips? Tighten slightly. Major leaks? Disassemble and reseat washers.
Common Mistakes to Avoid
| Mistake | Consequence | Fix |
|---|---|---|
| Using two separate P-traps | Creates airlock, slow drainage | Use one shared trap with continuous waste |
| Incorrect slope | Water pools, causes odor | Maintain ¼” per foot downward slope |
| Overtightening joints | Cracked plastic, leaks | Hand-tight + ¼ turn max |
| Ignoring venting | Gurgling, siphoning | Ensure existing vent is functional |
Should You Hire a Plumber?
While this is a manageable DIY project for most, consider professional help if:
- Your local code requires permits or inspections
- The existing drain line is corroded or misaligned
- You’re unsure about venting or trap arm length
According to HomeAdvisor (2025), the average cost to re-plumb a double sink without disposal is $150–$350, versus $50–$100 in materials if DIY.
FAQ Section
Q1: Can I use the old disposal drain pipe for the new setup?
A: Only if it’s part of a properly configured continuous waste system. The disposal’s outlet is typically offset and lacks a side inlet for the second sink. You’ll likely need a new wye or cross tee fitting.
Q2: Do I need a new P-trap after removing the disposal?
A: Yes. Disposals often use a specialized “disposal flange” that doesn’t match standard strainers. A new 1½” P-trap kit ensures compatibility and proper sealing.
Q3: Why is my sink draining slowly after the change?
A: Likely causes: incorrect slope, double trapping, or partial clog. Verify that only one P-trap serves both sinks and that the horizontal pipe slopes continuously toward the drain.
Q4: Can I connect a dishwasher after removing the disposal?
A: Yes—but you’ll need an air gap or high-loop installation. Most dishwashers connect to the disposal for anti-siphon protection. Without it, route the drain hose up to the underside of the countertop (high loop) before dropping into the sink drain.
Q5: Is ABS or PVC better for under-sink plumbing?
A: Both work. PVC is more common in the U.S., slightly stiffer, and uses solvent cement. ABS is black, impact-resistant, and glued with special cement. Never mix them—use matching materials throughout.
Q6: How long does this project take?
A: For a beginner: 2–3 hours. For experienced DIYers: under 90 minutes. Allow extra time if replacing old corroded pipes.
Conclusion
Re-plumbing a double sink after removing a garbage disposal isn’t just about connecting pipes—it’s about ensuring safe, efficient, and code-compliant drainage. With the right tools, clear steps, and attention to detail, you can complete this project confidently and avoid costly mistakes.
Now that your sink is flowing smoothly, why not share your success? Tag a friend who’s tackling a kitchen upgrade or share this guide on Pinterest or Facebook to help others avoid plumbing pitfalls!
And remember: great plumbing isn’t seen—but it’s always felt (in the form of no leaks, no smells, and fast drainage!). 💧🔧
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