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How to Fix a Toilet – Parts – Flange


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Toilet Flanges and Sewer Inlets

Many people are unfamiliar with the drain line of a toilet because it is located under the floor and out of sight. The drain line, and most of the plumbing in a house, are made from a durable material called Acrylonitrile Butadiene Styrene, or what is commonly referred to as ABS plastic. This type of piping material replaced the old cast iron pipes of earlier days. The drain line is comprised of three main parts that connect the toilet to the sewer feed in the street: the toilet flange, the sewer inlet, and the sewer line.

The toilet flange, which is sometimes referred to as a sewer, or closet flange, can be secured to either cement or wood sub-flooring. This part is located directly under the base of the toilet and connects the toilet to the top of the sewer inlet. The toilet flange is what physically holds the toilet in place and therefore must be securely attached to the sewer inlet and the floor. The toilet flange is usually a metal ring and an ABS coupling combined, but can also be made of plastic, and cast iron.
Toilet flanges come in a variety of sizes so that they can be connected to a range of different sewer inlets. The sewer inlet is what links the toilet flange to the sewer line. Most sewer inlets are made from an ABS fitting called an elbow or L; this is because of the 90-degree angle that is required directly below the toilet, so the sewer inlet can connect to the home’s sewer lines that run horizontally along the floor.
All elbow connections are female/female, meaning that both sides of the elbow will fit over a male pipe. A “Street Elbow”, on the other hand, has one female connection and one male connection. Whenever there is an elbow that has this male/female connection, it will be referred to as a “Street Elbow” or “Street L.”

Each size of an elbow, street L, and toilet flange yields several different possible connections. It is recommended that the sewer inlet in the bathroom be a 4-inch male connection adjoined to a 4-inch female toilet flange. When assembling this unit from scratch use the largest flange possible on a 4-inch opening so that in the future several quick replacement and repair options will be available. Given that most residential homes are plumbed with 3-inch ABS lines, a 3 to 4-inch street L is often used.

For example, here is a 3 to 4-inch Street L. Since it is called a Street L, the numbers 3 and 4 are referring to its different connection widths. The flanges that can connect to this inlet are a 4-inch female flange and a 3-inch female flange. The 4-inch female flange is the best connection because it is the largest and therefore provides more replacement options. Notice if a 4-inch female flange is used then a 3-inch female flange can be inserted in the future if the original flange breaks. The following is a list of other possible connections that can be found.

This sewer inlet is called a 3-inch Street Elbow or Street L. The name “Street” once again implies that the connection changes from a 3-inch female to a 3-inch male. The type of flange that would fit this connection would be a 3-inch female flange. Here is a 3-inch elbow having a 3-inch female connection at both ends of the pipe. A 3-inch male flange can be inserted to make the connection.

Here is a 4-inch elbow having a 4-inch female connection at both ends of the pipe. A 4-inch male toilet flange can be inserted to make the connection.

Here is a 4-inch Street Elbow or Street L. This inlet has a 4-inch female connection at one end and a 4-inch male connection at the other end. A 4-inch female toilet flange and a 3-inch female toilet flange can be inserted to make the connection.

When a flange is securely mounted to the sub-flooring or slab, a wax ring is placed on top of the flange to create a watertight seal between the flange and the toilet. Afterwards the toilet mounting bolts are slid in place; then the toilet is installed and the base is bolted to the flange creating a solid foundation.

In older houses, sometimes the sewer inlet will be too close or too far away from the wall for a modern toilet to be installed. In order to prevent having to move the sewer inlet a couple of inches in any direction, an angled toilet flange was created. The angled flange allows the toilet to be mounted a few inches from where the actual sewer inlet in the floor is located. It is a good idea to try an angled flange before attempting to move the sewer inlet by hand.



  1. I check a lot of woodworking handbooks. These one from WoodPrix are the best.

  2. You can learn more about it on woodprix webpage.

  3. If you are looking at flanges, you should examine the brand new BLACK MOLD ON HOLD technology that includes a sealed-bottom, watertight toilet flange with drain ports for water to go right back down. Amazing stuff. Created by Barracuda Brackets.

  4. Ewwww! Get that carpet out of the bathroom! GROSS!!!

  5. Carpet around a toilet? That makes no sense…

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