Is soapy or dirty water bubbling up into your kitchen sink whenever your dishwasher runs? This frustrating plumbing issue is more common than you might think and is usually a sign of an underlying problem with your drainage system.
Fortunately, the expert plumbers at Saffer Plumbing are here to help you troubleshoot the reasons your dishwasher is backing up into the sink so you can get back to cleaning your dishes effectively and maintaining a hygienic, fully functional kitchen.
Why Does a Dishwasher Back Up Into the Sink?
Most of today’s dishwashers don’t drain directly into your home’s main sewer line. Instead, they are connected to your kitchen sink’s drain either by a small nipple on the side of your garbage disposal or a special Y-branch tailpiece on the sink’s drain pipe. Because of this setup, any clog or obstruction in the sink drain, garbage disposal, or the dishwasher’s own drain hose can force that excess water to back up into the sink basin.
Top Reasons for Dishwasher Backups and How to Fix Them
Now, let’s explore the most common culprits behind soapy or grimy water backing up into your sink when the dishwasher runs.
1. A Clogged Garbage Disposal
Since the dishwasher often drains directly into the garbage disposal unit, any food debris, grease, or foreign objects clogging the disposal will also block the path of the dishwasher’s wastewater. The water will then reverse course and emerge in the sink.
An easy way to tell if the garbage disposal is the reason behind the backup is noting whether the sink is slow to drain, even when the dishwasher isn’t being used. If you’ve also heard a gurgling sound from the drain or recently put fibrous, starchy foods (like potato peels, celery, or coffee grounds) in the garbage disposal, a clog is a likely suspect.
How to Fix It:
- Safety First: Before you do anything, turn off the power to the garbage disposal. You can do this via the switch on the wall and by unplugging the unit under the sink. For added safety, turn off the corresponding breaker at your electrical panel.
- Check for a Blockage: Using a flashlight, look down into the disposal. If you can see a visible obstruction (like a piece of silverware or a large food chunk), use pliers or tongs to remove it.
- Use the Manual Crank: Many disposals come with a small Allen wrench (or you can use a standard one) that you can use on a hexagonal hole at the very bottom of the unit. Insert the wrench here and manually turn the blades back and forth. This can help dislodge tough clogs.
- Flush the System: Once you’ve cleared the clog and restored power, run cold water and turn the disposal on. Let it run for a minute to flush out any remaining debris. Then, try running the dishwasher again on a short rinse cycle to see if the problem is resolved.
- Get Professional Repairs: If the disposal is still not draining well, it may need to be professionally serviced. You can call Saffer Plumbing for effective garbage disposal repairs.
2. A Blocked Dishwasher Drain Hose
The flexible, ribbed hose that runs from your dishwasher to the sink drain is another common culprit behind a dishwasher backing up into the sink. Over time, food particles, grease, and detergent residue can build up inside this hose, creating a stubborn clog. You will know if the dishwasher drain hose is the problem because the backup happens exclusively when the dishwasher is running. Your garbage disposal and sink drain seem to be working fine otherwise.
How to Fix It:
- Locate and Disconnect the Hose: Find the drain hose under your sink. It’s usually a gray or black plastic hose. Place a bucket or shallow pan underneath the connection point to catch any water. Use pliers to loosen the clamp holding the hose to the garbage disposal or sink drain and disconnect it.
- Clear Any Clogs: Shine a flashlight into the end of the hose. You’ll likely see a buildup of gunk. You can try to clear it using a wire coat hanger that you’ve straightened out.Â
- Thoroughly Flush the Hose: For a more effective clean, disconnect the hose from the dishwasher as well (consult your dishwasher’s manual for instructions). Take the hose outside or to a bathtub and use a garden hose or faucet to flush it out with high-pressure water.
- Reconnect Securely: Once the hose is clear, reattach it to both the dishwasher and the sink drain according to the dishwasher’s manual.
3. A Clogged Sink Drain
Sometimes, the problem lies with the sink’s P-trap — the U-shaped pipe under the sink. This pipe is designed to hold water to block sewer gases, but it’s also a prime location for clogs to form from an accumulation of hair, soap scum, and grease.
If the P-trap is the problem, water will drain slowly from your sink all the time, not just when the dishwasher is running. You may also notice foul odors coming from the drain.
How to Fix It:
- Clear the P-Trap: Place a bucket under the P-trap to catch water and mess. Use a pipe wrench or large pliers to loosen the two slip nuts holding the trap in place. Once loose, you can usually unscrew them by hand.
- Clean It Out: Remove the pipe and empty its contents into the bucket. Use a brush and hot, soapy water to thoroughly clean the inside of the trap.
- Reassemble: Put the P-trap back in place and tighten the nuts. Hand-tightening is often sufficient, but you can give it a final quarter-turn with the wrench to ensure a good seal. Run water in the sink to check for leaks.
4. An Obstructed Air Gap
If you have a small, cylindrical fixture on your countertop near the faucet, that’s an air gap. Its job is to prevent a siphoning effect that could pull contaminated sink water back into the dishwasher. If this air gap becomes clogged with debris, it will block the dishwasher’s drainage path. When the dishwasher is running, you may notice water leaking around the base of the air gap.
How to Fix It:
- Remove the Cover: Pull off the metal or plastic cover of the air gap. It should come off with a gentle twist and pull.
- Clean the Interior: You’ll see a smaller plastic cap inside. Remove this as well. Clean out any food particles or gunk you find inside the air gap assembly using a small brush or paper towel.
- Reassemble and Test: Put everything back together and run the dishwasher.
When to Call a Professional Plumber for a Dishwasher Backup
If you’ve tried these troubleshooting steps and the backup persists, or if you’re not comfortable performing any of these tasks, call in your local plumbing experts. You may be dealing with a more severe clog deep within your home’s plumbing lines that requires specialized equipment like a motorized drain auger (snake) or hydro-jetting.
Let Saffer Plumbing Solve Your Dishwasher Drainage Problems
If your dishwasher is backing up into your kitchen sink, seek help from the licensed plumbers at Saffer Plumbing right away. Ignoring the issue or continuing to run your dishwasher while problems persist can lead to bigger plumbing headaches down the road.
Our team is equipped with the tools and expertise to handle an array of kitchen plumbing problems. We’re especially great at quickly and accurately getting to the bottom of why dishwashers back up, and we’ll provide you with the right solution that keeps future issues at bay, whether that’s a simple drain cleaning, a cost-effective plumbing repair, or a full garbage disposal replacement. Reach out to us today to book a service and restore order to your kitchen!