What Is Code For Kitchen Sink Drain Size? An Ultimate Guide

5/5 - (1 vote)

If you are renovating your kitchen, it’s essential to know the local codes and regulations regarding the plumbing system. The kitchen sink drain size should be one of the first to check. 

So what is code for kitchen sink drain size? Is there anything else to know about setting up the drain? Before starting your installation project, please check this guide first. 

We will explore the standard size for kitchen sink drains and some variations that apply to your case. Let’s dive in!

What Is Code For Kitchen Sink Drain Size? 

The code for the kitchen sink drain size, which measures about 3 ½ inches of diameter, is the plumbing code. With that drain size, you need a pipe size of around 1 ½ inches. 

Checking with your local regulations about the code is crucial as it differs from region to region. Some codes may require a large drain size for commercial and heavy-duty purposes. 

What Is Plumping Code?

The plumbing code is a set of rules issued by city, state, or federal governments. These regulations govern the planning, construction, and upkeep of plumbing systems in facilities.

The IPC highlights all technical information about plumbing regulations. And 35 states follow this rule, while others adopt the UPC. Depending on your state, you must obey either the IPC or UPC. 

In some ways, plumbing codes and traffic rules are similar. Although there are minor variations, they generally all contribute to secure, efficient flow within your facility. 

Of course, rules are set for us to follow. If you break any of them, you will risk getting into trouble with building inspectors.  

Are Kitchen Sink Drains Popular?

Yes. The kitchen sink drains are about 3 ½ inches, while the diameter of the bathroom drains measures around 1 ¼ inches.

Kitchen drains have a universal size because they will help with your kitchen setup. For example, if you install a drain of the wrong size, you will encounter blockages, water contamination, as well as other plumbing issues. 

As a result, the sizing system aims to meet your specific needs when setting up your kitchen sink. It also aids in waste system management.

Learn the plumbing code when setting up your kitchen drain system
Learn the plumbing code when setting up your kitchen drain system

What Size Will Your Drain Pipes Be?

The most common sizes for drain pipes are 1 ½ inches of diameter. Older drain assemblies and sinks often have about 1 ¼ inches smaller pipes. 

1 ½-inch pipes can fit most modern kitchen drains. The pipes are in charge of connecting your P-trap to your primary drainage pipe

Yet, some houses use up to two-inch pipes. Hence, you should use the reducing bushing for linking the lines. 

For example, a reducing bushing of 1 ½ to two inches can fit one end of the kitchen drain (1 ½ inches) to the end of the primary drain pipe (two inches).

What is the common size of the drain pipe
What is the common size of the drain pipe?

Do Kitchen Sinks Have A Cleanout? 

Maybe yes. The plumbing structure of your house or building will determine if your kitchen sink has a cleanout. 

The cleanout is a cap that helps you access the kitchen drain pipe easily. Then you can get rid of any blockages in the system. 

If there is a cleanout in your kitchen, it must stay near the kitchen sink or on the sewer line. But in other cases, you don’t need a cleanout because your kitchen sink drain lines are small and easy to clean with a plumber’s snake. 

How To Choose The Right Pipe Size For Kitchen Sink Drain? 

Aside from the code, you must consider other factors to choose the right pipe size for your kitchen sink drain. Here is what to check: 

State’s Housing Code

Each state has a particular housing code outlining the basic plumbing requirements. Hence, learn the regulations before buying the pipes. 

Plumbing Standard

The plumbing standard claims that a 1 ½-inch pipe can match most kitchen drain sinks. Although it’s not compulsory, most plumbers choose to follow it. 

Water Supply 

You might need a bigger pipe to handle the volume of water flowing into your kitchen sink. In addition, if your water pressure is powerful, a larger pipe could be necessary to stop water from splattering out of the basin.

So let’s make a comparison here: A 1 ½-inch pipe handles about three gallons of water per minute, while a two-inch pipe can transfer up to six gallons. So, if the water pressure and volume in your system are high, choose a larger pipe.  


A P-trap under the sink will keep sewage gasses out of your house. Therefore, the right size of the drain pipe also depends on the P-trap, which is from 1 ½ to three inches.  

Horizontal Drain Pipe

This pipe will run from the primary sewer line to the P-trap. The most common size for it is from 1 ½ to two inches.  


The pipe material will also affect your decision on the pipe size. For example, PVC pipes are often 1 ½ inches of diameter, while the joints are 1 ¼ inches.  

Clogged Pipes 

Choose a bigger one, such as two inches, to minimize the risk of your pipe getting clogged. The blockages won’t annoy you, then.  

Choose the right pipe size for your kitchen drain sink
Choose the right pipe size for your kitchen drain sink

Now you have chosen the right drain pipe size. Please check this video to learn the best way to install it:


The plumbing code is one of the most important things to check when setting up your kitchen drain sink. Then, consider the factors mentioned above to decide on the pipe size. 

Hopefully, this article has helped with your kitchen sink setup. For any further information, please feel free to ask. Thank you for reading!