How to Cap Off Dishwasher Drain on Garbage Disposal

Whether you’re redesigning your kitchen, introducing a new kitchen appliance, or adjusting your current setup, understanding how to cap off the dishwasher drain on a garbage disposal is important.

Navigating through kitchen plumbing might seem like a daunting task, but with a comprehensive guide and the right tools at hand, it becomes much easier. In this article, we’ll guide you step-by-step on how to cap off your dishwasher drain, ensuring it is properly installed, doesn’t leak, cause damage, or create a messy situation in your kitchen.

The process involves disconnecting the dishwasher hose from the garbage disposal, capping the drain, and then capping the inlet. While it might sound challenging, it can be accomplished with ease given the right tools, a bit of patience, and following our step-by-step guide.

What Is A Knockout Plug?

In the realm of kitchen appliances, a knockout plug plays a critical role. It is a plastic or metal cap pre-installed used to plug the drain holes. Its primary purpose is to seal the dishwasher inlet when the garbage disposal is used without a dishwasher. This helps in preventing any debris or water from entering or leaving the inlet unexpectedly.

However, if you wish to connect a dishwasher to your garbage disposal, the knockout plug becomes a hindrance and needs to be removed. Removing it allows the dishwasher drain line to enter the garbage disposal, creating a pathway for the dishwasher’s wastewater.

Removing a knockout plug can be a bit tricky, especially for beginners. But with the right instructions, you can do it with relative ease. We will delve deeper into how to remove a knockout plug later in this article.

Lamprey Hardware #1-5 Universal Rubber Plug

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Capping Off the Drain With a Rubber Plug

Capping off the drain is an essential step when you are disconnecting your dishwasher from the garbage disposal. Using a rubber plug is one of the simplest and most effective ways to achieve this.

The first step involves locating the dishwasher drain on your garbage disposal. This is where the dishwasher hose connects to the garbage disposal. Once located, you need to disconnect the dishwasher hose. Make sure to place a bucket nearby before you begin, as there might be some residual wastewater that could spill out.

After you’ve successfully disconnected the hose, it’s important to clean the pipe properly. This involves removing any debris or residue that might interfere with the sealing process. Once you’ve cleaned the pipe, it’s time to cap it off.

Select a rubber plug that fits snugly within the pipe. The diameter of the plug should match the pipe’s interior diameter to ensure a secure fit. Insert the plug into the pipe and use your wrench to secure it tightly. The rubber material is highly effective in forming a tight seal, preventing leaks and ensuring the drain is effectively capped.

Capping Off the Inlet With a Dishwasher Connector Kit and a Copper Cap

Alternatively, you can cap off the dishwasher inlet using a dishwasher connector kit and a copper cap. This method, although slightly more complex, provides a secure way to cap off the dishwasher inlet and prevent any leakages.

Like with the previous method, start by disconnecting the dishwasher hose from the garbage disposal. Always remember to keep a bucket nearby to collect any leaking water. It’s better to prevent a mess than to clean up after one.

Once the hose is disconnected, the next step is to remove the dishwasher connector. After that, you’re ready to attach the copper cap to the dishwasher connector kit. Make sure to follow the manufacturer’s instructions to ensure proper assembly.

Once assembled, secure this new component onto the dishwasher inlet. For this task, you will require your wrench again to tighten and secure the assembly. This ensures a leak-proof seal, keeping your kitchen dry and the connection secure.

What is the Purpose of the Dishwasher Inlet?

The dishwasher inlet on a garbage disposal provides a convenient and direct connection for wastewater from the dishwasher to flow into the disposal unit. This eliminates the need for a separate drainage pipe, simplifying the kitchen plumbing setup.

However, if you are not using a dishwasher or if it’s not connected to the garbage disposal, this inlet needs to be kept closed. A cap is used to prevent wastewater from the garbage disposal from entering the sink, which could lead to unpleasant odors or even potential clogs. Hence, understanding how to cap off this inlet becomes crucial.

How to Remove the Knockout Plug from a Garbage Disposal?

The knockout plug, while an essential component, can be an obstacle when connecting a dishwasher to a garbage disposal. Thus, knowing how to remove it is a valuable skill. However, it’s worth noting that this step requires patience and precision.

Start by locating the dishwasher inlet on your garbage disposal model. This should be a small hole where the dishwasher drain line is meant to connect. Once located, insert the screwdriver into the hole and gently tap the end with a hammer. The aim is to dislodge the knockout plug, pushing it into the garbage disposal.

Don’t be alarmed if it seems stuck initially. A few gentle taps should be enough to dislodge it. Once it’s inside the garbage disposal, you can easily remove it by either shaking the unit or using pliers.

Cons of Connecting Dishwasher and Garbage Disposal

Connecting a dishwasher directly to the garbage disposal does offer convenience and simplifies your kitchen’s plumbing system. However, it’s not without its potential issues.

When the dishwasher and garbage disposal are connected, larger food debris from the dishwasher can enter the garbage disposal. This can potentially cause clogs and affect the performance of the disposal. If the disposal is clogged or filled with waste, the water from the dishwasher cycle may not drain correctly, causing it to back up or overflow. This can lead to a potential leak, messy situation, or damage to your appliances.

Therefore, if you are considering this setup, make sure to maintain regular cleaning of both your dishwasher and garbage disposal to prevent clogs and build-up. Also, it would be best if you used the appliances in a manner that reduces the possibility of overflow. For instance, ensure that the garbage disposal is free from waste before starting a dishwasher cycle.


Kitchen plumbing might seem like an intimidating task to most, but with the right guidance and tools, you can cap off the dishwasher drain on a garbage disposal quite easily. In this detailed article, we explored the methods involving a rubber plug and a dishwasher connector kit coupled with a copper cap. Both methods have their own advantages and can provide a secure, leak-proof seal to your dishwasher drain.

Remember, it’s important to ensure your appliances are properly installed and maintained to prevent leaks and potential damage. Regular maintenance can also help increase the longevity of your kitchen appliances, helping you to avoid expensive replacements. But if these tasks seem overwhelming, don’t hesitate to hire a professional. Their expertise can save you time, and ensure the job is done correctly and safely.

Remember, whether you’re a seasoned DIY enthusiast or a beginner, patience, careful reading, and safety should always come first. Your kitchen is an important space in your home, and caring for it can result in a smoother household routine and a happier living environment.

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