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Toilet Rough-In Size Explained

1-Piece Toilet Install

Buying a toilet may seem like a simple purchase for most - after all, it’s just a toilet, right? WRONG.

Before you make your purchase, take a moment to consider how often your toilet gets used. Toilets are one of the most frequently used appliances in anyone’s home, especially family households, so you want to make sure you are buying the right one. In this blog, we touch on the #1 mistake that people make when purchasing a toilet – failing to consider their toilet’s rough-in size.

To avoid this mistake from occurring, we’ve put together a list explaining toilet rough-in sizes and how to measure them so that you don’t end up with an extra toilet that doesn’t fit in your home.

What Is Rough-In Size?

A toilet’s rough-in size refers to the distance between the toilet’s floor drain or waste outlet and the back wall behind the toilet. If your toilet’s rough-in does not align from the toilet to the finished wall behind it, then the toilet won’t fit. In most cases, toilets can’t be returned once unpackaged. That’s why it’s so important to consider your toilet’s rough-in size before you make your purchase.

The standard dimension for toilet rough-ins is 12 inches. However, this number can vary based on what type of home you live in. In older homes, you may encounter 10” and 14” rough-ins. Typically, 10” rough-ins are found in smaller bathrooms and half baths, while 14” rough-ins are found in larger bathrooms.

Toilet Rough-In Sizes, Measured

Now that you know how important it is to account for toilet rough-in size, we’ll walk you through the steps to make sure you are measuring your rough-ins properly.

Measuring Rough-In Without a Toilet

When a toilet is not yet present, measuring the rough-in size can be done with ease. Here are the steps:

  1. Identify the location of the toilet’s drainpipe or flange opening on the floor. You should see a round hole cut out from the floor (sometimes has white plastic lining around it).
  2. Measure from the bare wall to the center of the drainpipe or flange opening.
  3. Double check. If your measurement comes out at a number other than 10” or 12”, then it is possible that you measured incorrectly. When measuring, it is important to make sure that you are going from the bare wall to the center of the drainpipe – no further, no less.

Measuring Rough-In with a Standard Toilet

Is your toilet already in place? No problem! On your toilet, there is a visible base of bolts and caps that you can measure from. In some cases, there is even a visible profile where the trap way path can be seen. Here’s how to measure rough-in with a toilet already present:

  1. Look for small bolts or caps at the base of your toilet to identify where the toilet connects to the floor. Most often, these can be located in the trap way on the back left and right sides of the fixture. Once located, we recommend using painter’s tape to remind yourself of where you’ll be measuring from.
  2. Measure from the wall to the center of the toilet’s base bolts. This will provide you with the toilet’s rough-in size.
  3. Check your work. If your measurement is coming out to a number other than 10”, 12”, or even 14”, then you might be measuring incorrectly.

Measuring Rough-In with a Corner Toilet

As you probably could’ve guessed, measuring rough-ins in corners can be a bit trickier. Follow the steps below to see how we measure rough-ins in corners at BEST Plumbing:

  1. Locate where the toilet connects to the floor. Look for caps or bolts at the base of the toilet.
  2. Next, you’ll want to locate the toilet’s flange or drainpipe. Because the toilet is already in place, you will have to estimate where the drainpipe is based off of the center point between the bolts you located in Step 1.
  3. Use painter’s tape to mark the location of the toilet flange. You can locate this somewhere between your toilet seat and the tank.
  4. Measure from the toilet flange to the walls on the left and right side of the toilet at a perpendicular, 90-degree angle. We recommend using a carpenter’s square to get the exact angle. The spot where both measurements intersect at the midpoint of the toilet flange indicates what the rough-in size is. Both measurements should be identical.

Measuring Rough-In with a Wall-Mounted Toilet

In wall-hung toilets, the drainpipe passes through the wall rather than the floor. To measure rough-in size for wall-mounted or rear-mounted toilets, you’ll need to measure vertically from the bare floor to the center of the waste drain.

Choose BEST Plumbing to help with your toilet installation.

Still confused about toilet rough-in sizes? Don’t want to do the work by yourself? That’s where BEST Plumbing can help. At BEST Plumbing, our team of licensed plumbing professionals can help you find the optimal toilet to match your bathroom and fit your needs. Contact us today to get started!

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