Bathroom Sink Plumbing Rough-In Heights and How To Install

Working on the plumbing in your bathroom can be daunting, but if you are a master at DIYing, you can get it done with no problem. The layout is the hardest part since you can find such varying information circulating the internet.

The best option is to read the installation instructions of the specific sink you plan to install. If you don’t have access to that, read further to get the general bathroom sink plumbing rough-in heights.

Bathroom Sink Plumbing Rough-In Heights

In short, general bathroom sink plumbing rough-in height should look like this:

  • Sink drain: 18 to 20 inches from the floor
  • Hot water supply: 20 to 22 inches from the floor and 4 inches to the left of the drain
  • Cold water supply: 20 to 22 inches from the floor and 4 inches to the right of the drain

It’s a good idea to research the type of sink you will want and the rough-in heights for that specific sink. You can usually find this information in the installation instructions.

What Is a Plumbing Rough-in?

A plumbing rough-in is the skeleton of the plumbing system. The rough-in typically happens before the drywall or flooring is complete, where you are only working with studs and subflooring. During a bathroom sink rough-in installation, you will need to drill a larger hole for the sink drain and two smaller holes for the water supply lines. 

Why Do My Rough-in Heights Need To Be Correct?

Rough-in heights are very important; you shouldn’t try to guess or eyeball them. Most houses need to pass an inspection to make sure their plumbing is up to code. These inspections ensure that you have built a sink that works well and will not cause issues in the future. 

Bad plumbing can lead to a few different issues in your sink. It can cause weird noises and smells, slow draining, and bad water pressure. If the bad plumbing goes on long enough without service, it can lead to broken pipes and water damage, high water bills, and mold and mildew. 

What Factors Should I Consider When Figuring My Rough-In Heights?

Why are there so many contradicting opinions on the internet about rough-in heights? Different types of sinks, plumbing styles, and pipe lengths can lead to different measurements. There are a few different factors you should consider when calculating your bathroom sink rough-in heights. 

Unfinished Wall or Floor

If you have unfinished walls or floors, you will need to factor that into your rough-in measurements. Finished drywall or flooring can add up to half an inch to final measurements. Thus, you should add an extra half inch when you measure rough-ins in an unfinished space. 

Height of Sink

Before you even start measuring in your bathroom, you will need to decide how tall you want your sink to be. If you are a family of tall people, you might want it to reach about 36 inches. If you have a lot of kids in the house or someone who is in a wheelchair, you may want a shorter sink at about 30 inches. 

You will want your sink drain to fall around 12 inches below the base of your sink. You can put the drain very low and adjust the P-trap to fit, but putting the drain too high can be a difficult fix. 

So for a 36-inch sink, you would want to place the drain 18 inches from the floor. For a 30-inch sink, it may need to be closer to 12 inches from the floor. 

One thing to keep in mind is that it is better to go low than high. You will have more options if you end up wanting to replace the sink with a lower sink. The only limit to how low your drain can be is that your P-trap usually needs to be shorter than 24 inches. 

Type of Sink

Once you decide the height you want for your sink, you can start deciding which type of sink you want to install. This will determine its width, which we will discuss more in the next section.

A vanity sink has counter space around the sink. This is nice if there’s not much other storage space in the bathroom. The vanity-style sink can vary in width and height based on customer preference. These vanities can range from 30 to 36 inches high and just about as long as you want. 

You can install the wall mount sink at just about any height since it just needs to be low enough to connect to the drain and water supply lines. The standard is 30 to 36 inches as well, but again, it’s very customizable.

The last option for sink types is the pedestal sink. Pedestal sinks range from 29 to 34 inches tall, and they are not very customizable. If you are measuring for a rough-in and choose a pedestal sink, you will need to do a little more research before you start measuring.

Some pedestal sinks come with cut-outs in the back of the pedestal to hide the P-trap and water supply lines. If that is the case, you will need to consider that before you start placing the drain. 

Width of Sink

You will also need to consider the width of your sink or vanity as well as the distance you want to place it from the wall when you measure for rough-in pipes. You will need to place the pipes at the right height, but you will also need to place them at the correct distance from the wall to create good spacing. 

For example, a 24-inch vanity sink that you place 12 inches from the wall will require a drain 24 inches from the finished wall. Remember to add that half inch if working with unfinished walls. 

Keep in mind that your drain pipe should always fall directly in the middle of your sink with the water supply lines 4 inches on each side of the drain and 8 inches apart from one another. 

Wall Plumbing vs. Floor Plumbing

There are two options for rough-ins for a bathroom sink. You can either do wall plumbing or floor plumbing.

Wall plumbing is where the plumbing runs through the walls to both supply water and drain water. All of the pipes run in the walls and up into the ceiling.

If you decide to go with floor plumbing, you would drill all of your drain holes and supply holes in the floor, and your pipes would run underneath the subflooring. 

There are advantages and disadvantages to both methods. Wall plumbing is easily accessible, but you should not use it on exterior walls. During the winter, the pipes could easily freeze and burst, causing water damage to your home.

Floor plumbing is harder to reach after finishing the house, but it is safer in colder climates to protect against freezing pipes

What Are the General Bathroom Sink Plumbing Rough-In Heights?

If you don’t know what sink will go in the bathroom and just want to know the general heights for the drain and water supply lines, there is a standard in the industry.

The sink drain is usually 18.5 to 20.5 inches up from the unfinished floor and about 12.5 inches in from the unfinished wall. 

The water supply lines can go to two separate places, depending on whether you are doing floor plumbing or wall plumbing. 

For wall plumbing, the holes should go 2 inches above the drain, about 20.5 to 22.5 inches from the unfinished floor, and 4 inches on either side of the drain. The hot water line should go 4 inches to the left of the drain, and the cold water line should go 4 inches to the right. 

For floor plumbing, you should measure 4 inches on either side of the floor hole that will hold the drain in place. Then, measure 3 inches out from the wall at those 4-inch marks. At this point, the holes will be 8 inches apart from each other and 3 inches from the wall. 

Hiring a Professional

If this seems confusing, there is no shame in hiring a professional for help with bathroom sink plumbing rough-in heights. They have extensive experience with this and can complete the work much faster. It also may be worth it to pay the money, even though it may cost a little more than DIYing, for the sake of a quick job done right. 

The rough-in plumbing for a sink can cost anywhere from $300 to $5000. You can save money by calling a few different plumbing companies to get quotes on how much it will cost you to rough in a bathroom sink. You may find a deal that will be cheaper than doing it yourself!

Final Notes

Hopefully, this guide has provided you with the information you need to work on the plumbing in your bathroom. If you’re confident in your skills and have the correct rough-in height information, you should be able to get all the work done easily.

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