What Size Drain Pipe Do I Need For A Garbage Disposal?

Garbage disposals are a convenient addition to any kitchen. They make cleaning dishes, pots, and pans much more manageable. Instead of meticulously scraping off each chunk of leftover food, simply rinse it into the disposal. Flip the switch, wait for the garbage disposal to grind the leftovers, then shut it off. Tada – just like that, the food waste is taken care of!

If you’ve decided to commit to installing a garbage disposal, there are a few things you’ll need to know. After you purchase the system itself, you’ll need to buy the correct size plumbing and accessories to hook it up. This article reviews what size drain pipe you’ll need for a garbage disposal, so continue reading to learn more!

Do You Need A Special Drain For A Garbage Disposal?

Sink Drain

Yes, many garbage disposals require a specific sink drain flange. This consists of the metal disk at the drain entrance at the bottom of the sink and a short length of pipe that extends beneath the sink. The drain attaches to this pipe. 

All garbage disposals are designed to fit all kitchen sinks, given that the standard drain hole size for a kitchen sink ranges from 3.5 to 4 inches in diameter. A connection bracket fits on the base of the disposal’s basket strainer, which should be installed on the sink before the disposal is fitted into place. 

The bracket allows the disposal to connect and clamp into place underneath the strainer on a similar diameter hole. Food and water go straight through the drain, moving through the disposal before proceeding to the sink’s drain plumbing. 

What Size Is The Discharge Pipe On A Garbage Disposal?

Garbage disposals generally have a 1 ½ inch tailpiece designed to connect to your kitchen drain’s plumbing. If you connect the garbage disposal to a dishwasher, there will be two lengths of drain hose: one from the dishwasher and one from the tailpiece to the garbage disposal.

The factory drain hose comes on the dishwasher, which runs from the dishwasher to the smaller of the two tailpieces on the air gap. On the other side of the tailpiece on the air gap, there’s a ⅞-inch (inside diameter) hose that feeds from the air gap to the dishwasher nipple on the garbage disposal. 

The entire drain assembly between the dishwasher, garbage disposal, and kitchen sink are interconnected, sending wastewater out of the same drainage pipe. 

How Do You Install A Garbage Disposal?

Moen GXS75C Host Series 3/4 HP Continuous Feed Garbage Disposal with Sound Reduction, Power Cord Included

Installing a garbage disposal unit isn’t hard but can be confusing if you don’t know what you’re doing. The entire installation process generally takes two hours or less, depending on how quickly you move through the steps. 

We outline the process in our guide, “How To Plumb A Single Bowl Kitchen Sink With Disposal.” The process is relatively straightforward but may take a bit of know-how. If you’re entirely unfamiliar with plumbing, you might want to pass this project on to a licensed professional. 

There are a few different drain variations used for garbage disposals, including:

  • Drain line connected to the garbage disposal through an air gap
  • Drain line connected directly to the drain through an air gap
  • Drain line situated in a “high loop” to the disposal
  • Drain line situated in a “high loop” directly to the drain

If you decide to install the garbage disposal by yourself, make sure you check local codes before starting. Some areas have specific codes that don’t allow disposals due to limits on sewer capacity. Other areas may require air gaps if the disposal is used in tandem with a dishwasher. 

Additionally, some areas don’t allow plumbing work to be done by anyone other than a licensed professional. 

Frequently Asked Questions (FAQs)

What Size Garbage Disposal Do I Need?

InSinkErator Garbage Disposal with Cord, Badger 5, 1/2 HP Continuous Feed

Garbage disposals come in several different sizes, ranging from ⅓ hp to larger than one hp. The best size for you depends on your household: how many people there are, how frequently you use the kitchen, etc. 

We review several different garbage disposal sizes here.

Is An Air Gap Necessary For the Garbage Disposal?

Yes, generally, you need an air gap with your garbage disposal. The air gap helps prevent cross-connections and contamination that can happen with waste or discharged dirty water. However, specific rules and regulations vary from one area to the next. 

So, while some areas may require an air gap, others may not. That said, air gaps are usually a good idea with a garbage disposal, as they help keep your drinking water safe and prevent cross-connections and contamination. 

Read more about garbage disposals and air gaps here.

Do I Need A Garbage Disposal With A Dishwasher? 

Nope, you don’t necessarily need a garbage disposal with a dishwasher. The same concept applies the other way around. Generally, dishwashers are the more common appliance, so you usually don’t find garbage disposals without a dishwasher. 
That said, you can use either of them without the presence of the other. We discuss this topic more in-depth here.

1 thought on “What Size Drain Pipe Do I Need For A Garbage Disposal?”

  1. I have a Century youre Old house… Apparently the drain is not standard size… The hole in the sink… Any suggestions? Do I have to just replace the whole thing? If so, what would you recommend?


Leave a Comment