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What Is Code For Kitchen Sink Drain Size?

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Although plumbers are often portrayed in a less than glamorous light, their work is vital in making our homes so convenient. Running water makes life easier, but the job of fitting the right size pipes to each home is not as easy as you might think. If you browse the IPC, you’ll understand why plumbers charge for what they do, as the specification is highly technical.

If you want to determine the proper kitchen sink drain size, there are many things you need to keep in mind. This article will give a brief overview of the general concept of plumbing codes and the specifics of kitchen drains.


What Is The Plumbing Code?

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The International Plumbing Code (IPC) outlines the technical details surrounding plumbing codes. Thirty-five states have adopted the IPC, but those that have not generally have adopted all or at least part of the Uniform Plumbing Code (UPC). Your kitchen sink’s plumbing needs to remain compliant with these codes in your area.

Plumbing codes are very similar to traffic codes in several ways. They help ensure safe, efficient flow and are often comprehensive, although there are minimal (but important) differences depending on the region. In addition, if you repeatedly violate these regulations, you will get in trouble with the police (building inspectors) of the plumbing world.

Since a building inspector can flag a plumbing system for illegal use until the issue is resolved, it’s vital to meet the plumbing codes in your area. If you are unsure if your kitchen sink plumbing system meets local codes, check with a local licensed plumber or your local building department.


Is There A Universal Kitchen Sink Drain?

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Yes, today’s kitchen sink drains are universal. They are typically 3½” in diameter, larger than bathroom drains which are 1¼” in diameter. Kitchen sink drains are the same size as most standard-size shower drains.

This size is intentional, as it meets the specific needs of kitchen sinks. The drain and waste system is an important component of the kitchen sink and is usually the general culprit for code violations. It is assumed that the drain or vent assembly is improperly installed. In this case, it can lead to blockages, dangerous sewer gas releases into your home, water contamination, and plumbing problems elsewhere in your home.


What Size Should The Drain Be?

Kitchen sink drains converge into a series of pipes underneath the sink that whisk away the draining water. Generally, these pipes are made of PVC and are 1 ¼ or 1 ½ inch in diameter. The 1 ¼ inch tailpiece attached to the drain is usually found in older sink and drain assemblies.

Most modern drains are usually fitted with a 1 ½ inch outlet pipe. This section of the drainpipe connects the P-Trap to the main drain. However, some homes have 2″ drains so you will need a pressure reducing sleeve to connect these pipes. You will need a 1.5″ to 2″ reducing sleeve to fit the 1.5″ end to the kitchen drain and the 2″ end to the main drain in your home.

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What Is A Cleanout?

Your kitchen sink may have a cleanout, which is a removable threaded cap that allows you to easily access the drain and clear the blockage with a drain snake. In most cases, these are required on the horizontal branch of the drain. However, because the P-trap has a removable connection, it can be used as a temporary cleanout, so many homes do not have an additional cleanout under the sink.

However, you may be able to find a cleanout under the sink, as this depends on where the sink is located in the overall drainage system. Often, if there is a cleanout under the sink, it serves the main drain, not just the sink.

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Can I Use A 2″ Pipe For The Sink Drain?

We discussed this question a little in our last answer. Typically, a 1.5 inch PVC pipe is used for sink drains as it can adequately handle the flow of water from the kitchen sink. The two-inch pipe is usually used to steep out the water from the washing machine or shower. However, it can also be used as a vertical stack for the kitchen sink.


What Is The Minimum Diameter Of The Pipe Used To Discharge Waste Water?

The minimum diameter of a pipe for escorting wastewater is 4 inches. Generally, it is used as a building drain under the floor or in a crawl space to move wastewater out of the home to a septic tank or sewer.

In addition, if dealing with two or more bathrooms, a four-inch pipe may be an option to use. Professional plumbers and home inspectors use a pipe sizing chart to determine what size pipe is appropriate for what area.



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