What Is Code For Kitchen Sink Drain Size?

What Is Code For Kitchen Sink Drain Size

Anthony Barnes

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The role of a plumber is undoubtedly critical in making sure that our homes run smoothly in the most convenient way possible.

Running water makes our lives far easier, but the work that is required to properly fit a drainage system in each household should not be underestimated.

This is why plumbers typically charge a large amount for their services, as the technicality behind what they do should not be underestimated.

There are numerous codes that they follow when determining the correct sized piping or drain for your sink, and there are several things that they need to bear in mind.

This article outlines the ins and outs of plumbing code and how it specifically relates to your kitchen drain. 

What Is Plumbing Code?

What Is Plumbing Code

Plumbing code, otherwise known as The International Plumbing Code or IPC, is a coding system that outlines the technicalities of plumbing regulations.

The vast majority of the states have incorporated the IPC, but those who haven’t will at least implement an element of it in the form of the Uniform Plumbing Code or UPC. 

The plumbing within your kitchen sink (see also ‘What Are The Best Kitchen Sinks?‘) needs to stay in compliance with these specific regulations within your state. In this sense, plumbing codes are not dissimilar to traffic laws and regulations.

These codes help to ensure that the water supply remains safe and flows efficiently across the state, despite any minor differences dependent on your local area.

In addition, if you consistently violate these regulations, you will run into trouble with building inspectors, who can easily flag a plumbing system and render it illegal to operate until these issues are solved.

Therefore, it is critical that you meet the regulations in your area and thus, if you are unsure whether your kitchen sink is compliant, you should consult with a plumbing professional to ascertain this. 

Are The Drains On Kitchen Sinks Universal?

Yes, the drains on kitchen sinks are universal. They tend to be 3 and a half inches in diameter, are usually larger than most bathroom drains, which tend to be approximately 1 and a quarter inches in diameter.

The drains on kitchen sinks (see also ‘Why Does The Kitchen Sink Gurgle When The Toilet Is Flushed?‘) are also usually a similar size to most shower drains. 

This sizing was intended to meet the specified needs of each kitchen sink. As a drainage and waste system is a critical aspect of your kitchen sink, it usually occurs the most code violations.

If the components of your drain aren’t properly installed, this may cause dangerous blockages that can lead to the release of harmful gasses into your home, as well as water contamination. 

What Size Should My Drain Pipe Be?

The drain pipe on your kitchen sink (see also ‘How To Plumb A Single Bowl Kitchen Sink With Disposal‘) will feed into a number of pipes that are located beneath the sink. These pipes whisk away any water that has been drained from the sink.

These pipes are usually made of PVC and are approximately one and a half inches in diameter. If you have an older sink, there may also be a tailpiece attached to the drain. 

The vast majority of modern drains on a kitchen sink are fitted with an outlet pipe that is approximately one and a quarter inches long. This specific section ensures that the drainage pipe is connected to the p-trap (see also ‘S-trap VS P-trap (Traps Made Simple)‘).

Although, some homes will have longer drain pipes that are approximately two inches long and thus, you’ll need to implement reducing bushing in order to connect the lines properly. 

Does My Kitchen Sink Have A Cleanout?

Your kitchen sink may also contain a cleanout. A cleanout is a threaded cap that allows you to access the drain pipe easily in order to remove any blockages that may occur.

These can easily be removed using a drain snake that can be rented or purchased from stores like Home Depot. 

However, because the p-trap often has removable connections, it can also serve as a cleanout, so most themes do not need to operate an additional cleanout underneath their sink.

Whether a cleanout exists under the sink typically depends on the position of the sink itself. Usually, if there is a cleanout situated underneath the sink, it is for the purpose of the main drain pipe and not just the sink itself. 

Am I Able To Use A 2-Inch Pipe For Sink Drains?

Am I Able To Use A 2-Inch Pipe For Sink Drains

Usually, a one and a half inch PVC pipe (see also ‘How To Cut PVC Pipe As Pro’) is adequate for sink drains, as it can effectively handle the water flow out of your sink.

However, a two-inch pipe can be used in order to whisk excess water from shower stalls or washers. Although, if essential, it may also be used as a vertical stack within a kitchen sink. 

What Is The Minimum Diameter Of Pipes Needed For The Appropriate Drainage Of Waste Water?

The minimum size required to remove any waste water is four inches. This is typically used as a building drain that runs underneath floors in order to remove waste water from the home into the sewer or septic tank.

In addition, a four-inch pipe could be the appropriate diameter-length if you have more than two bathrooms.

A home inspector or professional plumber will be able to assess the right diameter needed for your individual household. 


To conclude, the code for kitchen sink drain (see also ‘How To Remove Kitchen Sink Drain‘) size varies from state to state.

However, most states will adopt the IPC or International Plumbing Code in order to ensure that regulations are being kept, and no dangerous blockages occur in the drainage system.

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By Anthony Barnes

Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age