--- title: "How to Open Dishwasher Drain on Garbage Disposal" canonical: "https://thekitchenmix.com/how-to-open-dishwasher-drain-on-garbage-disposal/" author: "Ava Mixwell" published: "2026-10-05T06:00:00+00:00" modified: "2026-10-16T13:03:53+00:00" language: "en-US" site: "The Kitchen Mix" description: "If you’ve ever stared at the side of a new garbage disposal wondering how to open the dishwasher drain on garbage disposal, you’re not alone. That little…" categories: "Kitchen Appliances" attribution: "The Kitchen Mix (https://thekitchenmix.com/)" --- # How to Open Dishwasher Drain on Garbage Disposal If you’ve ever stared at the side of a new garbage disposal wondering how to open the dishwasher drain on garbage disposal, you’re not alone. That little plastic plug hiding in the inlet port stops you cold, and the manual often just says “remove the knock-out” without showing you what that actually looks like. Manufacturers like InSinkErator and Waste King have shipped millions of disposals with this plug pre-installed, and the removal method changes depending on the model year and brand. Per the Uniform Plumbing Code (UPC), the dishwasher connection must be made to a dedicated inlet on the disposal or a separate air gap. Most modern disposals include that inlet, but it’s sealed from the factory to prevent leaks if you’re not hooking up a dishwasher. As of 2026, the most common plug style is a press-fit plastic knock-out, though threaded versions and thin metal discs still appear on older units. Let’s walk through exactly what you’re looking at under the sink and how to get that plug out safely. ## Quick Answer Locate the dishwasher inlet on the side of the garbage disposal. It’s a small circular port with a plug. Identify the plug type: knock-out, threaded, or thin metal disc. For a knock-out, insert a flathead screwdriver into the slot and tap with a hammer until it pops out. Remove any plastic debris. Attach the dishwasher hose and secure with a hose clamp. ![how to open dishwasher drain on garbage disposal](https://thekitchenmix.com/wp-content/uploads/2026/09/how-to-open-dishwasher-drain-on-garbage-disposal-mtzbcgmv.webp) *Image source: Bing (Web (fair-use with source credit))* ## Why This Step Confuses So Many People The confusion comes down to one thing: you can’t see the plug clearly from above. The disposal sits deep under the sink, often blocked by the sink basin itself, and the inlet port faces sideways or slightly downward. Even with a flashlight, it’s easy to mistake the plug for part of the housing, especially if the disposal is black or dark gray. Another layer: the words in the manual don’t match reality. “Knock-out” sounds like you should be able to just whack it, but some plugs are threaded and require turning, not pounding. Others have a thin metal disc that needs prying, not punching. If you apply the wrong force, you can crack the disposal body or strip the threads. Aggregate reviews on plumbing forums show that the #1 DIY mistake is hammering a threaded plug until it breaks. That turns a 5-minute job into a disposal replacement. The second most common error: failing to remove leftover plastic shards inside the disposal, which rattle around during operation and can jam the impeller. The good news? Once you know which plug style you’re dealing with, the rest is straightforward. You just need to shine a light and look for the telltale signs. ![dishwasher inlet port](https://thekitchenmix.com/wp-content/uploads/2026/09/dishwasher-inlet-port-mtzbchxp.webp) *Image source: Bing (Web (fair-use with source credit))* ## What You’re Actually Looking For (Visual Identifiers) Find the dishwasher inlet port. It’s a raised circular bump on the side of the disposal, usually about 1 to 1.5 inches in diameter. The port is located roughly midway up the disposal body, often on the side opposite the electrical connection. It may have a small sticker or a plastic cap covering it. Inside that port, you’ll see one of three things: - **Knock-out plug**, a solid plastic disc that sits flush with the inner wall. It may have a small dimple or slot in the center. This is the most common type on InSinkErator Badger and Compact series. - **Threaded plug**, a plastic or metal plug with visible threads. It has a hex indentation or a slot for a screwdriver. Common on Waste King L-8000 and some Moen disposals. - **Thin metal disc**, a flat, silver disc that looks like a coin. It’s often held in by a few small tabs. Found on older models and some budget units. Look for writing on the disposal body. Many models have “DISHWASHER INLET” or an arrow stamped nearby. If you see a round indent with no plug at all, the port is already open, you can skip this entire guide. ## Tools You’ll Need | Tool | Purpose | | --- | --- | | Flathead screwdriver (medium) | Prying knock-out plugs or unscrewing threaded plugs with slots | | Hammer (8–12 oz) | Tapping out knock-out plugs | | Allen wrench set (metric and SAE) | Unscrewing hex-type threaded plugs | | Flashlight or work light | Seeing the port clearly under the sink | | Bucket or towels | Catching drip water when you remove the hose | | Hose clamp screwdriver or nut driver | Tightening the hose clamp onto the dishwasher hose | | Pliers (optional) | Gripping stubborn threaded plugs if slot is stripped | Most of these you probably already own. The key is having a screwdriver that fits the slot or hex snugly, a loose fit will strip the plug. If you have an impact driver, don’t use it here; the torque can crack the housing. ## Step-by-Step: How to Open the Drain ### Step 1: Kill the Power Unplug the disposal from the wall outlet under the sink. If it’s hardwired, flip the circuit breaker. Never put your hand inside the disposal with power on. Even if you’re only working on the inlet port, the risk of accidental rotation is real. ### Step 2: Find the Inlet Port Shine your flashlight on the side of the disposal. Look for the raised circular bump. Clean away any grease or debris around it with a rag so you can see the plug clearly. ### Step 3: Identify the Plug Type Look inside the inlet. Is there a slot? A hex hole? A solid disc? Use the visual identifiers above to classify it. If you’re unsure, take a photo and compare with manufacturer diagrams online. ### Step 4: Remove the Plug **If it’s a knock-out plug:** Insert a screwdriver into the slot or dimple. Tap the screwdriver handle firmly with your hammer. The plug should pop inward into the disposal chamber. Do not hit hard enough to crack the housing, two or three moderate taps are enough. Remove the loose plug pieces from inside the disposal by reaching in with long-nose pliers. ![flathead screwdriver](https://thekitchenmix.com/wp-content/uploads/2026/09/flathead-screwdriver-mtzbciki.webp) *Image source: Bing (Web (fair-use with source credit))* **If it’s a threaded plug:** Insert the appropriate Allen wrench or screwdriver into the hex or slot. Turn counterclockwise to unscrew. It may be tight, use steady pressure, not jerking. Once it starts, unscrew by hand. **If it’s a thin metal disc:** Pry the disc out with a small flathead screwdriver. Be careful not to leave sharp edges. Sand down any burrs with fine grit sandpaper if needed. ### Step 5: Clear Any Debris Reach into the disposal through the sink opening (with power off) and feel for any remaining plastic shards or metal pieces. Remove them all. Even small bits can rattle or jam the impeller. ### Step 6: Attach the Dishwasher Hose Slide the dishwasher drain hose over the barbed fitting on the inlet. Push it on at least 1 inch. Secure with a hose clamp tightened snugly, not so tight that you crush the hose, but enough that it won’t pull off. ### Step 7: Test for Leaks Close the sink drain. Run the dishwasher through a rinse cycle. Check under the sink for drips around the connection. If you see moisture, tighten the clamp half a turn. If it still leaks, the hose may have a small cut, replace it. ## The Most Common Visual Mistakes (And How to Avoid Them) **Mistake 1: Confusing the inlet port with the reset button.** The reset button is usually located on the bottom center of the disposal, often red. The inlet port is on the side. They look nothing alike, but under poor light, people hit the reset button instead. That does nothing for the drain. **Mistake 2: Forgetting to remove the internal cap.** Some newer InSinkErator models (Evolution series) have a plastic cap inside the inlet that must be pulled out separately. If you only knock out the outer plug, the cap stays in place and blocks water flow. Look for a small disc deeper inside after the initial plug is gone. **Mistake 3: Leaving the hose clamp loose.** A clamp that isn’t tight enough will allow the hose to slip off when the dishwasher pumps out water. That means a flood under your sink. Always double-check the clamp tension. **Mistake 4: Using a hammer on a threaded plug.** This cracks the threads and ruins the housing. If you see threads, turn don’t pound. **Mistake 5: Thinking all disposals have a knock-out.** If you have an older model or a budget brand like Moen or Whirlpool, it may have a threaded plug or no plug at all (in which case you’ll need an adapter kit). Check the manual before forcing anything. ## What If It’s Not a Knock-Out? (Alternatives and Adapters) Not every garbage disposal comes with a straightforward knock-out plug. If you’ve removed the inlet cover and found a threaded plug, a thin metal disc, or nothing at all, you’ll need a different approach. **Threaded plug.** This is common on Waste King and some Moen models. It unscrews counterclockwise using an Allen wrench or flathead screwdriver. If it’s stuck, spray a little penetrating oil (like WD-40) around the threads and wait five minutes. Never use a hammer on a threaded plug. Cracked threads mean a new disposal. **Thin metal disc.** Older disposals sometimes have a metal disc held in by small tabs. Pry the disc out gently with a screwdriver. Smooth any sharp edges with sandpaper or a file. Metal fragments inside the disposal can damage the impeller, so vacuum them out. **No plug at all.** Some budget disposals lack a dishwasher inlet entirely. You might see a smooth bump with no opening. In that case, you need a dishwasher adapter kit. These kits include a barbed fitting that taps into the side of the disposal or attaches to the sink drain tailpiece. Follow the kit’s instructions carefully. Adapter kits cost $10 to $20 at hardware stores. **What if you have a dual-inlet disposal?** Certain InSinkErator Evolution models have two inlet ports: one for the dishwasher, one for a second appliance (like a reverse osmosis system). Only open the port marked for dishwasher. The other port is for additional uses, and removing its plug can cause leaks. **When you can’t identify the plug.** Take a clear photo of the inlet. Compare it with images on the manufacturer’s support page or installation manual. InSinkErator and Waste King both provide detailed diagrams by model number. The model number is usually stamped on the bottom or side of the disposal housing. If your disposal truly has no dishwasher inlet and no adapter kit fits, you can still connect the dishwasher drain. Use a sink drain tailpiece with a side inlet. This is a standard plumbing part that replaces the straight tailpiece under your sink basket strainer. It costs about $8 and accepts the dishwasher hose. This method meets code in most areas, but check local requirements. ## Frequently Asked Questions ### Do I need to remove the knock-out plug before attaching the dishwasher hose? Yes. The plug seals the inlet from the factory. If you try to push the hose over it without removal, water won’t drain. The plug must be removed completely, including any fragments inside the disposal. ### What happens if I don’t remove the knock-out plug? The dishwasher will fill with water and not drain. The pump may eventually burn out from running against a closed line. You might also see water pooling in the bottom of the dishwasher or hear a humming noise at the end of the cycle. ### Can I use a screwdriver and hammer on a threaded plug? No. Threaded plugs are designed to unscrew, not to be punched inward. Hitting a threaded plug with a hammer can crack the disposal housing or strip the threads. Use the correct tool: an Allen wrench or flathead screwdriver turning counterclockwise. ### Why does my disposal have two inlet ports? Some models offer dual inlets for connecting both a dishwasher and another appliance, such as a water filter or reverse osmosis system. Only open the port labeled for dishwasher use. Opening the wrong port can cause leaks or backflow. ### What if the plug breaks into pieces inside the disposal? Retrieve every piece before running the disposal. Use long-nose pliers or reach through the sink opening with a gloved hand. Plastic or metal shards can jam the impeller or rattle loudly during operation. Vacuum out any remaining debris. ### Do I need an air gap if I connect the dishwasher to the disposal? Local plumbing codes vary. Many areas still require an air gap device mounted on the countertop, even with a disposal connection. Check your local code before finalizing installation. If you skip an air gap where one is required, you risk backflow and failed inspections.