8-Inch & 9-Inch Rough-In Toilet Replacement Solutions

Written by

Paulk Webb


Freddie J. Hagopian

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8 inch & 9 inch rough in toilet replacement

In every bathroom remodeling project, it’s crucial that you get the right measurements for your new toilet system, or else it won’t fit. It’s even more challenging if you have an 8-inch or 9-inch rough-in because it’s rare to find that measurement in the market.

So, what’s the solution for an 8 inch & 9 inch rough in toilet replacement?

The cheapest way is to install a toilet offset flange. If you want to purchase a new potty system, opt for a 10-inch rough-in model, wall-hung, or rear discharge unit. You can also move the wall to fit a new rough-in toilet.

Let’s discuss more of these solutions below.

8” And 9” Rough-In Toilet Replacement Solutions

Installing an ill-fitted toilet in the bathroom can be a disaster. Here are a few tricks that you can do to solve your 8-inch and 9-inch rough-in toilet problems.

1. Install An Offset Flange


If you want a replacement for your 8-inch rough in toilet, you can use an offset flange to close the gap. The flange allows you to move the toilet closer to the finished wall by another two inches. With that in mind, you can use a 10-inch rough-in toilet model as a replacement for your original 8″ rough in toilet setup.

The fitting is crucial for your drain system. Generally, this type of flange fits a 3-inch or 4-inch drainpipe.

Installing an offset flange may require skills and tools. Here are the steps.

  • Remove the existing toilet, including the old wax ring and toilet flange.
  • As necessary, cut the sewage pipe down to fit the new flange snugly.
  • Set the offset flange onto the top of the sewage pipe.
  • Apply PVC cement to join the pipe and the flange together.
  • Fill the gaps with expanding foam and mount the bolts into the flange.
  • Install a new wax ring and a standard rough-in toilet.

2. Use 10-Inch Rough-In Toilets

Some 10-inch rough-in units aren’t exactly 10 inches in size. They leave a bit of clearance between the wall and the tank, making them a perfect fit for a toilet with a 9 inch rough in. To determine how much clearance is provided, look at the specification sheet of every product.

Here are the best 10-inch rough-in toilets that might fit a 9-inch rough-in.


  • Kohler K-3889 Highline Comfort Height: According to Kohler’s specification sheet, the two-piece toilet provides a 3/4 inch or 19 mm of clearance between the tank and the finished wall.

This makes the Highline ideal for rough-ins measuring about 9-¼ inches. Apart from that, the toilet also stands out with its chair height and lower water consumption (1.28 GPF).

  • Toto CST744SF.10#01 Drake: As seen in Toto Drake’s specification sheet, the two-piece elongated toilet leaves a gap of ⅞ inch or 21mm of clearance from behind the tank to the wall.

You can even get close to a 9-inch rough-in if you move the bolts on the toilet flange hole a little bit. Other things to expect from this model are a powerful GMAX flushing system and a universal height.

  • American Standard Cadet 3 Right Height: This two-piece toilet offers the highest clearance of about 1-⅛ inches from the wall to the tank. You can set this up in a 9-inch rough-in easily and enjoy a cleaner flush each time you use the toilet.

3. Try Wall-Mounted Toilets


The easiest way to solve the 8-inch and 9-inch rough-in issues is to ignore them altogether. Switch your floor-mounted toilet with a wall-mounted one that installs the commode off the floor. Since the waste line will be transferred inside the wall cavity, you have the liberty to choose any rough-in size.

The aesthetic of a wall-hung toilet is superior to other toilet types. These toilets save floor space and make cleaning a lot easier. Though the setup looks sanitary with a wall-hung toilet, it entails serious plumbing work.

First, you need sturdy drywall to affix your toilet with the correct wall mount toilet flange, mounting plate, and studs. Next, assemble the frame composed of bars and cistern. Complete the assembly with a waste pipe elbow, then attach the unit.

4. Opt For Rear Discharge Toilets


Another way of solving a nonstandard rough-in issue is to use a rear discharge toilet like the Swiss Madison SM-2T120 Calice. With this floor-mounted model, the drainpipe isn’t on the floor but on the rear part. This means no tearing of the bathroom floor.

There’s still some plumbing work to be done, but it’s not as much as a wall-hung toilet. You can keep your wall intact because you only need to connect the toilet to a 90-degree trap connector. Since the waste pipe rough-in is greatly reduced to four to six inches, it saves you a lot of work.

Keep in mind though that these rear toilets flush waste loudly due to high water pressure. The P-trap connector may also remain visible, so it can be an eyesore for some people.

5. Renovate The Wall


If you have the time and resources, why not renovate the wall to modify your nonstandard rough in toilet measurement? You can start from scratch and move the wall further to increase the rough-in distance to standard measurements like 10 or 12 inches.

This wall renovation project is easy if you work on a partition wall that’s made of a timber frame and wall studs. If it’s a load-bearing one, then it’s ideal to ask the help of a professional.

How to Measure Your Rough-In


Getting the precise rough-in is important if you want the toilet to fit into the drainpipe for efficient waste disposal. To measure the toilet rough-in, all you need is a tape measure.

Get the distance of the toilet rough in from the wall to the center of the drain pipe that’s located beneath the toilet. Make sure that you start on a bare wall without the baseboards and moldings. Note down the measurement in inches.

If the toilet is already installed, look for the base bolts that secure the fixture to the floor. Get the rough-in from the bare wall to the center of the bolts, which are either located on the left or right part of the unit.

Frequently Asked Questions


What to consider when replacing? Are there any requirements?

The most important consideration in replacing a new toilet is the rough-in dimensions. Get the right rough-in to ensure that the toilet expels the waste straight to the drainpipe. The standard rough-ins are 10 inches, 12 inches, and 14 inches.

The bowl shape is another factor to consider, whether you like a more comfortable elongated shape or a space-saving round one. The flushing system also matters to determine the toilet’s performance. Do you like a powerful siphon jet or a water-saving dual flush system?

What are the common issues and troubleshooting tips?

A common toilet problem is the sound of water running. When the water runs and the tank remains empty, check the tightness of the toilet handle. Check the condition of the trip lever and make sure that it’s connected to the guide arm securely.

When the water runs after you fill the tank, the culprit might be the flapper. Ensure that the flapper is secure and free of any rust.

For a toilet that doesn’t flush properly, adjust the water level. As for water leaks underneath the tank, check the inlet valve and refill tube.


At this point, I hope you know what to get for your 8 inch & 9 inch rough in toilet replacement. All of the solutions we presented above are great, but my favorite is the offset toilet flange because it’s affordable and easy to install. Regardless of your choice, make sure that the solution fits your space and budget.

Let us know your favorite solution in the comment section below. If you like this article, please share it with your friends.

Read more: How to measure a toilet for replacement?

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