Also, it gives you a general idea about the common height estimation of the sink drain pipe, p trap, and fixtures. However, we have decided to take it a step further. Instead of letting you know just about the common rough-in measurement for kitchen sinks, we have covered the topic in a broader range. If you are up for your next DIY plumbing project or kitchen remodel, we believe this article may help you.  

What Does the Term ‘Rough-In Measurement’ Mean?”

It is important to know what the term rough-in indicates in plumbing before the rough-in height of the kitchen sink. Rough-in is a plumbing stage in the kitchen or bathroom in which all the pipes are installed. 

This is a prior phase to putting the fixtures (like faucets, toilets, and sinks) in place, and also, all the pipes are not covered yet in this stage. It occurs after the basic construction framing is done, but the final plumbing fixtures are yet to be installed. Bear in mind that an inspection of the rough-in work must be done before installing fixtures to the pipes. 

The standard rough-in height for the sink typically indicates the common height of sink drain pipes. We will know it elaborately in the following section. 

Kitchen Sink Drain Pipe

A drain pipe starts from the sink’s drain opening and extends towards the P-trap. From the P-trap, a horizontal drainpipe extends either into the wall or through the cabinet floor. The horizontal pipe is connected to the main plumbing system, which ultimately carries wastewater away from the sink.

What Is The Rough-In Height For Kitchen Sink Drain?

The upper end of the kitchen sink’s drain pipe is connected to the sink drain opening. So, the rough-in height for the kitchen sink drain pipe measures from the floor to the point where the pipe is attached to the P-trap and extends up to the sink opening.

The standard height of a kitchen drain pipe is approximately 18-20 inches from the floor where it is connected to the P-trap. Then, the drain pipe may extend up to 24-28 inches to reach the sink drain, considering varying counter height for the sink. 

When measuring the rough-in height for a kitchen sink drain pipe, you should ensure that the height is not higher than the disposal outlet. Also, consider the size of the P-trap, which takes up some vertical space, and the counter’s height. 

According to the International Residential Code, the P-trap should hang at a maximum height of 24 inches below the drain. The P-trap and drain pipe should be fixed in a way so that there is enough space to remove the P-trap and clean it.

However, local building codes may dictate some specific requirements for plumbing pipes along with sink drain pipes to ensure safety and compliance with the building’s plumbing standards.

What Factors Should Be Considered When Measuring the Rough-in Height of the Kitchen Sink Drain?

Sink Type and Depth

Sink type and depth may affect the rough-in height of the sink drain. Deeper sinks make rough-in height lower and force the P-trap to be in the lower position. The standard depth of the kitchen sink is about 8 to 10 inches. So it wouldn’t be wise to go deeper than the standard depth of the sink unless it is necessary. 

The sink type also specifies the height marginally. For example, under-mount sinks may have different height requirements compared to top-mount sinks. So, be sure about any height requirement for your sink type.

P-trap Alignment

The rough-in height you measure should be aligned with the P-trap for proper installation. It’s essential to consider the size and height of the P-trap before assuming a standard rough-in height. 

According to the ICC digital code, the P-trap should not extend beyond 24 inches from the opening of kitchen fixtures like the sink. Therefore, ensuring that the P-trap is in the correct location is crucial.

Counter Height 

If the kitchen sink is installed on the countertop or at the height of the counter, then the height of the counter may also shape the height of the drain pipe beneath the sink. If the counter height is at a higher level for some reason, then the drain pipe’s height will also be higher. 

Conversely, if the counter height is lower, the drain pipe under the sink will also be positioned lower. So, consider the counter’s ideal height before measuring the sink drain pipe’s rough-in height.

The National Kitchen and Bath Association (NKBA) specifies that the ideal height of a countertop is 28″ to 45″ above the finished floor. However, the most common and ideal height for a kitchen sink counter is considered to be 36 inches from the floor. 

What is the Standard Size of the Drain Pipe Under the Sink?

The size of the drain pipe matters for proper drainage and preventing blockage inside the drain pipe. The standard size of kitchen sink drain pipe is 1.5 inches in diameter, which is most common in modern kitchen sinks and sufficient for handling normal sink drainage. However, larger pipes, such as 2-inch diameter, are also available. 

Using larger pipes sometimes can cause incompatibility issues with the sink drain, P-trap, and other fixtures and, therefore, may need an adapter fitting to connect. That’s why it is wise to stick around with the standard drain pipe size for the kitchen sink, which is 1 and ½ inches in diameter. 

However, the size you use depends on the local building code and other factors such as sink types and distance to the main line. For example, if the main drain line is pretty far away from the sink drain pipe, a larger pipe, such as a 2-inch pipe, may be more suitable. Before choosing a specific size, make sure of the compatibility, building codes, types of sink, and scale of application. 

Conclusion

The rough-in height of the kitchen sink drain can vary significantly, sometimes being as low as 12 inches from the finished floor. However, a lower height leaves very limited space for the P-trap. It can become quite challenging when you need to remove or replace the P-trap. 

Therefore, ensure that the drain pipe is positioned high enough to allow flexibility when installing or removing the P-trap. Additionally, aim to maintain the sink at the standard height of 36 inches, although it can range from 30 to 45 inches.