Toilet Flange Sizes & Types Guide

Ever had a loose toilet, probably wiggling, and leaks at the drain; then your toilet has a flange problem. Issues with a toilet flange are quite common as it’s what connects the toilet to the floor then the drain pipe. Unfortunately, a quick fix isn’t the solution, you have to consider the types and sizes.

Toilet flanges come in six different types and three standard sizes with the option of an odd fit. The types are based on the material from which they are made, that is aluminum, copper, brass, stainless steel, plastic, and cast iron. The sizes also range from a four by three, four-inch, or three inches flange.

Each of these choices has its features, advantages, and disadvantages. To understand more about them, here’s an in-depth look into the different types and sizes of flanges plus more information you may need to know about each category. But before we jump into that, let’s first understand what a toilet flange is and why its role is quite crucial.

What is a Toilet Flange?

A toilet flange also known as a closet flange is a mounting base or pipe fitting that securely fits the toilet to the floor while connecting the drain pipe to the drain sewer of the house. Derived from the old French word “flanchir” meaning to bend, the closet bend comes in a cylindrical shape and a flat base/ surface.

The flat surface will have a wax ring and a section where bolts or screws can be tightly fitted. The toilet will be mounted on top of the flange, rather than directly on the floor. While you can screw in the toilet to the floor, it’s safer and better to use the toilet flange in between to avoid leaks in the future.

Toilet Flange purpose and how it works
Toilet Flange- Photo:

What’s Its Purpose?

From the definition above, the flange will be used for two primary reasons;

  • To tightly secure the toilet to the floor
  • To connect the toilet to the drain pipe/ sewer.

Another reason the flange is important is to prevent leaks using its wax ring that seals gaps between the closet bend and the bottom of the toilet. Using the flange will also avoid damage to the floor during the installation of the toilet, at least you won’t have to directly drill the toilet to the floor.


There are six types of closet flanges to choose from;

Copper Toilet Flanges

Copper is known to be highly resistant to corrosion, making it extremely durable. They can be rigid or soft and flexible, it depends on your preference.

Copper Toilet Flange
Copper Flange

Soft copper flanges bend easily and can be easier to install than the hard type. Hard copper flanges will need elbow joints to allow you to effectively join them to the drain pipe. The elbow joints will aid in matching the space for a perfect fit.

Copper is a popular choice as it’s biostatic, meaning anti-bacterial, as well as antifungal; it’s not a good host for bacteria, fungi, or viruses. Therefore, it’s safer to use for plumbing as it delivers potable water components better than raw metal would.

Brass Toilet Flanges

Brass is an alloy of zinc and copper,  therefore very sturdy. It’s rust-resistant, highly corrosion-resistant, and malleable. They come in two ways, simple circular flanges, or those with elbow joints attached to allow for easy connection to the drain pipe.

Brass Toilet Flange
Brass Flange

Brass toilet flanges come in multiple shapes and sizes including regular, deep seal, and offset sizes. The material is also heat resistant making it very durable. Unfortunately, it’s very heavy and can oxidize upon exposure to air.

Plastic (PVC) Toilet Flanges

Polyvinyl chloride flanges are the most prevalent choice for closet flanges. It can be used for residential or commercial purposes, plus, they are the most affordable of the six. What makes it an excellent choice is how strong, durable, and rust-resistant it is. Furthermore, it’s lightweight.

PVC plastic toilet flange
Plastic Flange

An alternative to PVC is abs plastic which is equally light, but stronger and more durable. Costs more, but can handle bulkier waste or running water. Some types of plastic flanges are 100% plastic while a few have metallic tops used to make the wax ring. All PVC toilet flanges are manufactured to fit three-inch or four-inch drain pipes.

Plastic is a good choice however, they are more likely to give in to high pressure, even with the abs plastic that’s more resistant to heat, water, and shock.

Stainless Steel Toilet Flanges

Next up is the stainless steel closet bend that’s also rust and corrosion-resistant. It’s very durable and has a better seal than most flanges. Most of these stainless steel types, however, only means the wax ring material. Other than that, the rest of the flange can be made of cast iron, plastic, or copper.

Seeing that there are different types of stainless steel, the most common option is the 304 that contains approximately 8% nickel and 18% chromium. More advanced kinds have added silicone to minimize chances of oxidation. Luckily, the flange is lighter than the other metal types.

Cast Iron Toilet Flanges

Cast iron flanges are uniquely designed to only fit with cast iron pipes. They’re very strong, durable, come in multiple sizes including offset flanges.

Cast iron Toilet Flange
Cast iron Flange

They’re differently shaped with an elongated pipe made to fit even deeper into the drain pipe, what they call a deep-body cast iron flange.

It’s best utilized on drain pipes located lower than the sub floor. Similar to stainless steel, cast iron can come in different types, and unfortunately, this material rusts faster than any other metal.

Aluminum Toilet Flanges

Last, but not least, is the aluminum type. It’s light, corrosion-resistant, and sturdy. Used to make primarily the wax metal ring, but can also make the entire flange.

The best aluminum type is unadulterated aluminum, however, an alloy with copper, zinc, magnesium, or manganese can make it more durable.


Now let’s have a look at the different sizes of flanges depending on their shape and diameter.


There are three shapes used to design a flange;

  • Regular – they are designed to fit around and inside the opening of the pipe. They are a few inches deep into the drain pipe, say five inches.
  • Deep seal – these can reach way deeper than the regular kind, approximately 12 inches deeper.
  • Offset – these are convenient for strangely placed openings like when the pipe opening is far from the floor or too close to the wall. They will feature an elbow for easier adjustments and installation of the flange situated inches away.


You can slide the flange over the drain pipe or into the pipe. This is why there are only two diameters; three and four-inch flanges.

Standard 4×3

The 4×3 is a prevalent size that fits most toilets and is available in almost all hardware or plumbing stores. The 4×3 is an indication of two diameters; the top part that connects to the toilet, which is four inches, then the bottom diameter of three inches fitted to the drain pipe. The difference occurs where the three-inch bottom diameter is designed to fit with a 40 pipe used in most homes as the standard size drain pipe.

The 3-Inch Flanges

These flanges simply imply three-inch diameters on the top and bottom area. They are the easiest to install however, make sure your piping is sized properly. If it’s not a 3-inch pipe, consider using a different flange as this one may offset the glance and alignment of the plumbing job.

You could also find a four inches flange with four inches diameters at the top and bottom, but these are very rare compared to the three-inch closet flanges.

Odd Sized Flanges

There are oddly sized flanges that measure bigger or smaller than the standard 4×3 toilet flange. A good example is an ABS plastic flange with a 3 1/2-inch bottom diameter and a 7-inch top diameter. This will need extension kits to raise the height of the flange to fit its new installation requirements.

Others even have a diagonal set opening for additional space, especially for elongated towels replaced over a round toilet. There’s a need for the extension.

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