Standard Toilet Flange Dimensions (with Pictures)

Stacy Randall
by Stacy Randall

Have you ever wondered why your toilet wobbles from side to side or leaks at the base? The problem could be with your toilet flange, a ring that secures the basin with the floor drain. If you have a damaged or unlevel toilet flange, your toilet won’t sit flush and level with the floor.

Knowing which toilet flange to get can be an intimidating process, particularly choosing the right material and size. Once you find out the drain pipe diameter, selecting a toilet flange is much simpler. A typical toilet flange measures three inches diameter at the pipe and four inches in diameter on the top.

Most modern toilet flange installations use PVC plastic toilet flanges, as they are economical and easy to install. However, there are a number of other materials such as aluminum, cast iron, copper, brass, and stainless steel. To accommodate pipe setup and location, toilet flanges come in three different design shapes–regular, deep seat, and offset.

What Is a Toilet Flange?

A toilet flange, also known as a closet flange, is a pipe fitting that mounts the toilet to the floor. It also connects the closet bend to the drainpipe to let water and waste flow out. The toilet flange allows you to secure the basin without mounting directly onto the floor.

There are two main sizes for residential and commercial use: the 3-inch flange and the 4×3 inch flange. Since the drainpipe is typically 3 inches, the majority of toilet flanges available will meet this standard. However, there are other sizes for specialized areas and applications or to accommodate for non-standard piping or adjacent installations.

Regular Toilet Flange

3-inch Toilet Flange

The 3-inch toilet flange is the most precise of the flanges on the market. As its name suggests, it has a 3-inch diameter at both the top and bottom. You must match the 3-inch toilet flange precisely to avoid gaps and leaks after installation.

4×3 Toilet Flange

The 4×3 inch toilet flange is very popular because it allows flexibility of fit for the basin connection. This flange has a 3-inch diameter at the bottom and a 4-inch diameter at the top. The different diameters ensure the bottom joins with the drain pipe and any sized toilet basin.

The full 4×3 toilet flange unit stands 2 ¼ inches high. This measure combines the 1 ¾ inch pipe and the ⅜ inches flange thickness. The design allows it to sit inside the closet bend, and sit level with the finished bathroom floor.

4-Inch Toilet Flange

The 4-inch flange is less common, as standard 40 piping is the norm in most residential construction. However, if a house has two toilets on the same drain, a 4-inch pipe will be necessary. This flange measures a 4-inch diameter at both the top and the bottom.

The advantage of using the 4-inch toilet flange is that it allows flexibility for replacement down the line. Should the flange ring get damaged or break entirely, a 3-inch flange can easily sit inside of it. This is a much quicker repair option than a total replacement, and the new flange will function just fine.

Additional features on the 4-inch toilet flange are extenders, spacers, and a waxless ring. The extenders and spacers help you align the flange ring flush with the floor so the toilet can sit level. The waxless ring is a new alternative to the traditional ring, adhering directly to the toilet horn and closet seat.

Source: Amazon

Deep Seat Toilet Flange

A deep seat toilet flange has the same diameter measurements as any regular flange type. The difference lies in the pipe connector at the bottom that fits into the closet seat. The pipe on a deep seat toilet flange can extend as long as 6 inches.

You would use this flange as a repair option as opposed to a new installation. The long pipe barrel works with broken flange rings, compressed wax rings, or leveling with the floor. The extra length helps to properly secure the new flange and reinforce the connection.

Offset Toilet Flange

An offset flange allows for easier installation in older homes, where the drain may be too close to the wall. It maintains the traditional diameters in the pipe and barrel, but the barrel sits at a 45-degree bend. This bend shifts the toilet basin at the proper distance from the wall without adjusting the pipes.

The pipe barrel itself can measure 1.45 inches at the pipe junction and 3.25 to the flange ring. You’ll need to trim the waste pipe to fit the offset barrel, so the flange ring is level. Once installed, you should be able to seat the basin within the 10 to 14-inch standard rough-in measurements.

Offset toilet flanges that allow replacing round basins with extended basins feature a diagonal set opening. This diagonal set allows extra space to install the longer basin without any difficulty. The pipe length and diameter are not affected because the angled set rests closer to the flange ring.

Source: Amazon

Odd-Sized Toilet Flange

Occasionally, you may need an extension to connect the basin to ABS pipe or install an elongated toilet basin. Odd-sized toilet flanges have larger openings at the flange ring to accommodate any space concerns. The pipe diameter is still 3 inches, but the flange diameter can go as high as 7 inches in diameter.

RV Toilet Flange

Bathroom installation in recreational vehicles isn’t much different from residential setups. They use the same 3-inch or 4-inch piping and have standard 3-inch and 4-inch bottom diameters. The difference is that the top diameter is larger, measuring 7 inches in diameter.

For RV toilet flanges, there are wax ring models available for installation. However, since wax can melt in extreme temperatures, bolt or glue models are a better choice. Repair and replacement are much simpler since there’s no concrete subfloor involved.

Source: Amazon

All-In-One Installation Kit with Flange

Innovations in flange design and features have created simpler do-it-yourself options for flange replacement and repair. Danco’s All-In-One Installation Kit with Flange combines the flange and seal into one unit and includes no-cut bolts and spacers. Its outer diameter measures 4 ¾ inches, and its inner diameter measures 2 ¼ inches.

Source: Amazon

This kit is more of an extender and wax ring combination than a standalone flange ring. You’ll still need to install a standard flange directly to the closet seat opening. Once that’s in place, the kit adjusts to the necessary height and alignment and allows repositioning for an exact seal.

The extender works with flanges seated ½ inch above the floor or 1-½ inches below to ensure a level basin. Additionally, the bolts are adjustable to get the perfect length without needing to cut through metal. The kit also includes spacers in case the bolts don’t fully tighten and secure the basin install.

Source: Amazon

Related Questions

Can you shim a toilet?

A loose or wobbly toilet can break loose the wax seal or cause someone to injure themselves. Reseating the entire basin is time-consuming and might not even be necessary to level it off. Luckily, using simple shims can help with this problem and possibly be completed with fewer steps.A shim can be a thin tab made of plastic, rubber, or wood that can slide under the basin. Once you check for leaks and find the uneven spots, slide the shims in by hand and distribute them evenly. Be sure to loosen the bolts to ease shim insertion, and refrain from tapping the ends with a hammer.While it is possible to shim a new or leaking toilet, the steps involved nearly equal replacing the flange itself. If you have installed the basin and it’s still unlevel, shimming may benefit you. Otherwise, it would be best to reseat the flange and wax ring to provide an even resting surface.

How long should toilet flange screws be?

The toilet flange screws should be long enough to bore into the subflooring without the basin shifting or sitting unevenly. Determining this calls for knowing the base surface and thickness and the type of screw needed for the job. A good estimation would be 1-inch screws for shallow flooring and 1 ½-inch screws for thicker flooring.While it is always ideal to use the proper size screws, you can also use washers in a pinch. If you don’t have the correct screws and need to finish the repair, you can use some tightly fitted washers. This can help create a secure connection, at least until you can get the proper screws.

Can you use a toilet immediately after installation?

Theoretically, once the toilet basin is fully installed and tested, it’s immediately available to use. However, the wax seal needs time to cure and any silicone, caulk, or grout used. A good rule of thumb is to wait a few hours, depending on the sealants involved.Silicone or caulk needs to cure at least three to six hours after application before basin use. Likewise, grout can take twice that amount of cure time, requiring six to twelve hours to cure completely. Waiting for the adhesives to settle will protect the integrity of the seal for a longer time.You could use the toilet immediately if necessary, provided you don’t sit or put weight on the basin. A basin secured to the floor with bolts only is available for use, as well. However, this would not be the best idea, as sudden weight and shifting could loosen the wax ring.

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Stacy Randall
Stacy Randall

Stacy Randall is a wife, mother, and freelance writer from NOLA that has always had a love for DIY projects, home organization, and making spaces beautiful. Together with her husband, she has been spending the last several years lovingly renovating her grandparent's former home, making it their own and learning a lot about life along the way.

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