How to Connect a Dishwasher to a Garbage Disposal

Last Updated On June 11, 2024

Updated on April 25, 2023



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how to connect dishwasher drain hose to disposal (1)

Do you have a new dishwasher or garbage disposal you need to install? 

If you do, you must connect the two devices by running a hose from the dishwasher drain to your garbage disposal unit.

In this quick guide, we will walk you through the process so you can start using your new appliances. Let’s get to it.

4 Steps to Connect the Dishwasher Drain Line to the Disposal?

Your dishwasher should have a long flexible hose used as your drain pipe. This dishwasher hose allows you to connect the dishwasher and the garbage disposal.

The hose will run from the dishwasher to an air gap. Then from the air gap to the disposal.

1. Remove the knockout from the garbage disposal with a hammer and screwdriver. Then use pliers to remove the metal plug.

A garbage disposal is manufactured with a knockout. You must remove this knockout before connecting the garbage disposal to the dishwasher. Remove the plastic plug using needle nose pliers. (See the video below these steps for a visual.)

If you can’t remove the plastic plug, let it stay there. The garbage disposer will grind it up, but it will take a few days. 

2. Install the drain connection fitting and drain hose to the back of the dishwasher. 

The dishwasher will come with the drain hose connectors, the dishwasher drain hose, and a hose clamp for both the dishwasher and the garbage disposal. 

3. Feed the drain hose through the hole In the cabinet.

Before the dishwasher installation, you’ll need an opening for the drain line to get into the sink cabinet. You can use a drill with a hole saw or a paddle bit to create this access. 

4. Provide an L Loop in the line, route, and strap the drain hose into place.

Routing the dishwasher drain hose to the garbage disposal correctly is as important as the connections themselves. You should always give the wastewater a smooth path, free from any resistance. 

Siphoning is a concern when routing a dishwasher drain hose. Make sure you install a high loop in the drainage system. A high loop is when the drain hose comes out from a low area of the cabinet and gets secured higher than the hole in the garbage disposal.

This will help to keep the dirty water from your kitchen sink garbage disposal from flowing back into the washing machine.

 You might find these 2 videos helpful:

First, here’s a video of installing a dishwasher with garbage disposal:

Here is a video showing the dishwasher knockout itself:

Why Do We Need This Connection?

You don’t need a garbage disposal to use a dishwasher, but if you have one, it’s a good idea to make this connection. Let’s take a quick look at the why and what of this connection.

As your dishwasher runs through its cleaning cycles, it must drain the dirty water. This wastewater will have food waste from dirty dishes.

Running this wastewater into the garbage disposal unit can grind up those solid bits before sending them down the drain. This helps to eliminate drain clogs. 

It also means less rinsing of dishes before placing them in the newly set dishwasher.

What to Avoid When I Connect the Dishwasher Drain Hose to a Disposal

There are a few small steps you don’t want to forget when installing a dishwasher drain hose. 

  1. Garbage Disposal Knockout – If you forget to remove the knockout in the garbage disposal drain hole, your kitchen will flood.
  2. Poor drainage and siphoning – Drain lines require the least path of resistance and should have no low spots for standing water.
  3. Water damage – Any loose connections or cracks in the drain hose will leak. Even a tiny drip can cause water damage.

Final Thoughts on How to Connect a Dishwasher to a Garbage Disposal

While you can save money by connecting a dishwasher drain hose to the disposal yourself, all plumbing projects have risks. If you are uncomfortable doing this work, consider calling a professional plumber.

FAQs on How to Connect the Dishwasher Drain Hose to a Disposal

Do I need an air gap connecting the dishwasher drain hose to the disposal?

Yes, you will need dishwasher air gaps. Air gaps help prevent cross-contamination.

What happens if I incorrectly connect the dishwasher drain hose to the disposal? 

If it’s not done correctly, you may face leakage issues that can compromise your kitchen’s cleanliness. Moreover, dirty water and residual grease may flow back toward your dishwasher, causing possible contamination of your dishes. 

Don’t risk the potential hazards – ensure your dishwasher drain hose is installed correctly for peace of mind.

Why does my dishwasher drain hose need a loop?

This drain line loop is required by code. It prevents water from the waste disposal from flowing back into your dishwasher.

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About Plumbing Navigator

We write about "all things plumbing," helping you navigate common questions, repairs, and the best plumbing products on the market.

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We write about “all things plumbing,” helping you navigate common questions, repairs, and the best plumbing products on the market.

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