How to Measure Kitchen Sink Drain Size [Quick Steps]

A kitchen sink is an essential part of the kitchen. When replacing the sink drain or the whole sink, you have to measure the sink drain size. This is important to provide optimal water flow and flush, while also preventing any potential leaks.

That said, if you purchase a new kitchen sink, it might come without a drain assembly kit or instructions. Since you have to buy some parts separately, you need to know what to look for in the store. Even if you are not familiar with plumbing, our guide will explain how to measure the kitchen sink drain size.

In this article, we’ll also focus on proper rusty crumb cup replacement as well as the pipes on your existing sink. Prepare your measuring tape and check our quick overview of the process.

How to Measure Kitchen Sink Drain Size

How to Measure Kitchen Sink Drain Size:

Step 1: Check the instructions that came with the sink

The standard drain hole size that can be found on most kitchen sinks is 3-1/2 inches in diameter. Still, it is also possible to find 4-inch holes in some cases. This information should be written in the instruction that comes with the sink or drain assembly kit.

Step 2: Try to contact the manufacturer

If the kitchen sink you’ve purchased came without instructions, you can also try to call or email the manufacturer and ask a question about the product. For the products from the nearest stores, you can ask a manager for help. Sometimes this step won’t be possible, and you’ll have to measure everything manually.

Step 3: Measuring the sink drain with the tape

To check the kitchen sink drain size, take a tape and place it across the center of the drain hole. That way, you’ll get the maximum width between two opposite points. This also should be of the exact size of the drain strainer suitable for your sink. Once you’ve written down the parameters, you can try assembling the strainer to see if it fits.

Step 4: Check if the strainer fits in the drain hole

Place the strainer in the hole and screw the locknut to see if there is no gap. Don’t forget to attach the gasket using silicone adhesive when putting everything together! After you’ve measured the kitchen sink strainer and installed it, it’s time to switch our attention to a crumb cup.

How to Measure a sink drain opening for a crumb cup

At the first glance, it might seem that any crumb cup will fit the strainer. The truth is that crumb cups can have different forms and sizes. 

Step 1: Find the diameter of a drain circle.

Use a measuring tape to find out the diameter of a drain circle with the installed strainer. Like with the sink drain hole, place the tape across the center and write down the size. The next step contains information about the depth of the strainer.

Step 2: Find the depth of the basket

Place the end of the measuring tape closer to its edge right before it meets the slope. Don’t put the measurement tape’s end into the center because the strainer might not fit the entire construction. The same rule applies when looking for a regular plug instead, which is also known as a stopper. After that, you must learn how to avoid mistakes when buying a crumb cup or a plug.

Step 3: Get a suitable crumb cup or a plug

With the parameters that you’ve just collected, you can go to the nearest store and find a proper crumb cup. Remember to avoid buying a taller model. This will lead to having a gap between it and a strainer. Thus, the water won’t collect in the sink. Instead, it will go down the tailpipe.

How to Measure Sink Drain Pipes

Step 1: Measure the drain pipe

You start measuring from the wall where the drain pipe goes. Place the measurement tape right to it and go all the way to the nut that attaches to the P-trap. Also, keep in mind that you’ll need to add two extra inches to it. That’s because the pipe that connects to the waste line hides inside this wall. After, you’ll need to measure the waste pipe.

Step 2: Check if the waste pipe needs an adapter

You might have to connect pipes of different sizes. Measure waste pipe as it might require an adapter with a 2-inch diameter. As this step is over, you can proceed with the tailpipe.

Step 3: Measure the tailpipe

It is located right under the strainer’s locknut. This goes all way down to the P-trap nut. The next step will be measuring the P-trap.

Step 4: Measure the P-trap

The last thing to do is to measure the P-trap from the nut to the wall drain pipe. When you are done, it’s a good idea to check if your water supply line requires replacement as well.

Step 5: Check the water supply line

The procedure with the water supply line is much simpler because the pipes are flexible. That means that a couple of extra inches here and there won’t be a problem. All you have to remember is the proper diameter. Probably, you won’t even need the plumber’s tape when putting it together.

Once everything you’ve written down on paper, you can take everything apart and go to the store.

Step 6: Disassemble the drain pipes

In case you can’t measure some parts, it’s a good idea to disassemble them and take them with you. A shop assistant will be able to find a proper replacement in a matter of minutes. You’ll want to close the water supply line valve before disassembly for extra security. Don’t worry if you can’t find a drainpipe of the same length in the plumbing store. You’ll need to cut it to get the required length.

Step 7: Cutting down the pipes

The material these are made of is PVC, which is very easy to cut. In case you are not sure about the durability of this material, these pipes might last up to 70 years.

Now that you know everything about measuring kitchen sink drain pipe size, we can discuss the different pipe sizes currently available.

Standard Kitchen Sink Drain Size Code

When speaking about the kitchen sink drain pipe diameter, the standard kitchen sink drain size is 1-1/2 inches. This means the hole inside the pipe, not the actual diameter of them. With older kitchen sink drain pipes, you can come across the 1-1/4-inch size. The full size of the pipe is either 2 or 3-1/2 inches. Do you know what’s the rough-in height for kitchen sink drain?

As for the strainer, they all have a standard size at the top. The pipe that goes inside is much smaller, and it must match the tailpiece’s size. The tight seal is very important to prevent any leaks and ensure optimal connection.

Which drain pipe size do you need?

The tailpiece’s size will tell you what pipes you’ll need to look for in the store. For example, a 2-inch pipe is needed for a 1-1/2-inch drain hole. Alternatively, you’ll want to get a 1-1/2-inch pipe for a 1-1/4-inch hole.

These are the standards used in not only the state you live in but also all around the world. For more information, you’ll need to check the local plumbing codes. If you are still not sure about which parts to get, it’s recommended to call a professional.

Conclusion

The process of measuring a kitchen sink drain size can be done with a few quick steps. All you need is to grab the tape and follow the abovementioned steps while writing down the parameters.

Starting with the sink drain hole, you then move to the strainer with a crumb cup. Finally, you check the pipes and even disassemble some parts to take with you.

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