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What To Know Before Buying A Rear Outlet Toilet

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Buying a new toilet for your home is not an easy decision.

Not only do you have to consider different designs and colors, but there are actually multiple types of toilets that you will need to choose between. 

What To Know Before Buying A Rear Outlet Toilet

One of the most popular types of toilets is the rear outlet toilet.

But what is a rear outlet toilet and how does it work?

We have the answers to these questions as well as recommendations for the best rear outlet toilets, so read on for the information you need!

What Are Rear Outlet Toilets?

If you’re not sure what a rear outlet toilet is, it’s sometimes also called a back outlet toilet or a rear discharge toilet

Rear outlet toilets are different from standard toilet designs, which drain into plumbing in the floor.

Draining into the wall is more convenient for high-rise apartment buildings where it can be very complicated to direct plumbing through the floor. 

Another benefit of rear outlet toilets is that installing one doesn’t involve digging up your bathroom floor.

If you’re remodeling your bathroom and don’t want to have to damage your tiles, you may want to consider a rear outlet toilet. 

In fact, any unexpected toilet installation is likely to be easier with a rear outlet toilet because it’s much quicker and cheaper to make a hole in the wall than to pull up the floor and rearrange the existing plumbing. 

How Does A Rear Outlet Toilet Work?

We’ve explained roughly what a rear outlet toilet is, but how exactly does it work? 

In a rear outlet toilet, something called a P-trap is used to connect the wall hub fitting to the waste outlet.

Then, when the toilet is flushed, the waste is directed into the wall and then into the plumbing that connects to either a septic tank (see also ‘Cesspool Vs Septic Tank‘) or a sewer line. 

This is largely made possible through pressure-assisted flushes.

Pressure-assisted toilets have an additional tank that is called the pressure vessel.

This tank is filled with compressed air, which combines with the water from the toilet.

When you flush the toilet, the pressurized water flows into the toilet bowl and forces it through the waste outlet at a high speed.

While this is a louder flush system than regular flushes, it’s more powerful, which is how the water and waste are able to travel through the wall rather than through the floor. 

Rear Outlet And Floor Outlet Toilets

There are several significant differences between rear outlet toilets and floor outlet toilets that you should be aware of when choosing a toilet for your home. 

The first and most obvious difference is that a floor outlet toilet is positioned above a drainpipe and is mounted to the floor using a toilet flange, which connects to the drainpipe and keeps the toilet securely in place. The toilet base and the flange are both protected by a wax ring. 

A rear outlet toilet is also floor-mounted, but instead of using a flange to connect it to a drainpipe, it is bolted to the floor using bolts.

This is because rear outlet toilets dispose of waste through the wall instead of through under-floor plumbing. 

Rear Outlet Toilets And Wall Mounted Toilets 

What To Know Before Buying A Rear Outlet Toilet

Many people assume that rear outlet toilets are wall-mounted because of the direction in which waste is removed, but in fact, rear outlet toilets and wall-mounted toilets are two separate things. 

Wall-mounted toilets (see also ‘Wall-Mounted Toilet Problems And How To Fix Them‘) , as you might expect, are mounted to the wall behind the toilet.

This means that only the toilet bowl protrudes from the wall with no visible toilet tank.

If you’re wondering how this is structurally possible, it’s because wall-mounted toilets use frames called carriers to anchor the toilet to the wall.

Even so, existing walls often have to be made thicker or thick walls need to be built from scratch to accommodate these structures.

On the other hand, as we have already mentioned, rear outlet toilets are bolted to the floor, although they are not connected to an underfloor drain pipe like floor outlet toilets.

Rear outlet toilets can be one-piece or two-piece and the tank is always visible, unlike the hidden tanks of wall-mounted units. 

Rear Outlet Toilet Installation

We’ve covered the mounting differences between rear outlet toilets, wall-mounted toilets, and floor outlet toilets.

However, if you want to truly understand the installation process for rear outlet toilets, we’re going to explain it in more detail here. 

First of all, one-piece rear outlet toilets are generally easier to install than two-piece toilets.

Therefore, if you’re planning to install the toilet yourself and you don’t have any plumbing or construction experience, a one-piece rear outlet unit is definitely the best option.

However, if you do opt for a two-piece rear outlet toilet, the installation will involve fitting the bowl first and then mounting the tank, which takes longer and requires precise measurements to ensure that everything lines up properly. 

To install a rear outlet toilet, you will need the following: 

  • A screwdriver 
  • A drill (including a bit of the correct size)
  • Some PVC glue 
  • An adjustable wrench 
  • A deep-socket wrench
  • A compatible P-trap connector
  • A pencil 

Once you have gathered all the necessary supplies, the installation process goes like this: 

  1. Locate the bolts for your toilet tank and put a steel washer on each bolt, and then a rubber washer. The rubber bolt should always be on the side facing the toilet tank so that the ceramic doesn’t crack during tightening. 
  2. Find the bolt holes in the toilet tank and put the bolts into the holes. 
  3. Before securing the nuts onto the bolts, put another rubber washer and metal washer on the ends. 
  4. You will now take your deep socket wrench and hold the bolts in place while using the adjustable wrench to tighten the bolts. 
  5. Line up your toilet bowl so it’s in the position you want for installation. 
  6. Find your wall hub fitting and measure the space between this and where the toilet outlet ends. 
  7. Cut your P-trap connector to the corresponding size. 
  8. Trace around the base of the toilet bowl with your pencil and, using the same pencil, draw two marks on the mounting holes. 
  9. Take your drill and create the holes that you will use to bolt the toilet to the floor. You’ll need to drill the mounting holes for the tank as well at this stage if you’re installing a two-piece rear outlet toilet. 
  10. Put PVC glue on the connector and carefully insert it into the fitting that you measured earlier. 
  11. Put the waste outlet into the connector. You will need to lift the toilet to do this, so if it’s too heavy, please get someone else to help you. 
  12. Now you can put the bolts with washers on them into the mounting holes in the base. Use a screwdriver to tighten them. 
  13. Put the bolt caps on the ends of the bolts. 
  14. Take the tank gasket and secure it to the top of the toilet’s tank by putting both bolts into the bowl mounting holes. 
  15. Pass a rubber washer, a metal washer, and finally, a nut onto the bolt and tighten them using your adjustable wrench. You will need to do this from underneath the bowl. 
  16. At this point, you can also put the bolts and washers into the mounting holes in the toilet tank, tightening them in the same way. 
  17. Connect the toilet tank and the supply line for the water. 
  18. Turn the shut-off valve in a counterclockwise direction (this turns it on) so that the tank fills up with water. 
  19. To check that no parts of your toilet allow water to leak through, flush the toilet once or twice. 
  20. Put the lid on the toilet tank
  21. Secure the toilet seat (see also ‘How To Paint A Toilet Seat‘).  
  22. (OPTIONAL) Caulk the toilet base to ensure that water doesn’t collect beneath your toilet and make the installation look more professional. 

And there you have it! Your rear outlet toilet is installed!

Rear Outlet Rough-In Measurements 

What To Know Before Buying A Rear Outlet Toilet

We’re about to show you some of the best rear outlet toilets on the market, but before we do, a word of warning: 

When you’re choosing a rear outlet toilet for your bathroom, you need to pay close attention to the dimensions of the rough-in.

This is particularly important if you already have a rear outlet toilet that you want to replace with a new unit because, unless you want to do some time-consuming remodeling, you will need to make sure that your new toilet matches the space of the old one. 

If you’re not sure what we mean by ‘rough-in’, it’s the space between the floor and the center of the water outlet pipe.

Ensure that any measurements you take are taken from the floor in its finished state for the best level of accuracy. 

If you have experience installing floor outlet toilets, please note that the rough-in is not the same for rear outlet toilets.

The rough-in of a floor outlet toilet should be measured from the middle of the drainpipe to the wall at the rear of the toilet, unlike rear outlet rough-ins, which are measured from the floor. 

The Top-Rated Rear Outlet Toilets

Here are just a few of the best rear outlet toilets that you can buy for your bathroom right now!

We’ve outlined the key features of each unit to help you decide which one will fit better in your home. 

Kohler K-3652-0 Barrington

Key Features

  • Two-piece construction 
  • Elongated toilet bowl 
  • 4-inch rough-in measurement 
  • 31.5 (H) X 21.25 (W) X 29.25 (D) inches 
  • Pressure Lite flush 
  • WaterSense label 

Saniflo SaniAccess3

Key Features

  • Two-piece unit 
  • Available with elongated and round bowls 
  • Pumps 150 feet horizontal/15 feet vertical
  • 1.28 gallon economical flush
  • 31 (H) X 17.25 (W) X 28.5 (D) inches 

American Standard Yorkville

Key Features

  • Two-piece design 
  • Elongated toilet bowl 
  • 15-inch bowl height 
  • 4-inches rough-in 
  • 1.6 gallon flush 
  • 29.25 (H) X 20.5 (W) X 29.75 (D) inches 

Signature Hardware 941039 Ebler

Key Features

  • Two pieces 
  • Elongated bowl (15.5 inches high)
  • 6.5-inch rough-in 
  • 0.8 and 1.6 gallon flush options 
  • 30.75 (H) X 15.75 (W) X 26.5 (D) inches 


So far, in this article, we have explained what rear outlet toilets are and how they work.

We’ve compared them to floor outlet and wall-mounted toilets and explained how to install them.

We have also explained the importance of taking careful rough-in measurements. 

That’s a lot of information to take in, so if you need a reminder, here are all the pros and cons of rear outlet toilets: 


  • Less complicated to install in high-rise buildings. Because underfloor plumbing is difficult to work with in high-rise and apartment buildings, rear outlet toilets are usually the best choice for these buildings. That’s because they don’t need to be positioned above a drainpipe on the floor – all you need is enough wall space. 
  • Can be installed in various rooms. If you buy the right kind of rear outlet toilet, you can install your new toilet in basically any room. For example, if you need a toilet in your basement, you can buy an upflush rear outlet design that will pump the water vertically. 
  • No need for floor remodeling. Floor outlet and wall-mounted toilets usually require the bathroom floor to be rebuilt so that the plumbing can be accessed. With rear outlet toilets, this isn’t necessary.
  • More powerful flush. Because rear outlet toilets need to pump water in directions other than downward, they have flushes that are significantly more powerful. They usually use pressure-assisted flushes for maximum efficiency.


  • Loud flushes. The downside of having a more powerful flush is that there will be more noise each time you flush the toilet. The pressure of the water in the toilet bowl is responsible for most of this noise. 
  • Visible toilet connectors. No matter how well you install your new rear outlet toilet, you will always be able to see the P-trap connector. This is not ideal from an aesthetic perspective. 

Final Thoughts 

Thank you for reading until the end of our guide! We hope that it has been informative for you as a first-time rear outlet toilet buyer. 

If you’re living in a high-rise building and don’t know what kind of toilet to buy, we think you should definitely choose a rear outlet unit because the plumbing work is much less difficult.

Just make sure to measure the rough-in carefully and consider the benefits of one-piece versus two-piece toilets in terms of installation.

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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