How to add toilet plumbing to a sewer line

November 2, 2017Blog Standard

Toilets drain lines begin with a flange under the toilet. A flange is a tube with a flat circular base at one end with screw holes. The flange is pushed through a hole in the floor and connected to a 90 degree coupler. The coupling is connected to a drain line two inches in diameter. This sewer line is then attached to the existing sewer line (generally three or four inches in diameter) using a coupling with a two-inch pipe coming out to the side.


  1. Measure the diameter of the flange pipe and cut a hole in the ground a little larger than this diameter; Make sure the hole is placed in the correct place by following the installation instructions of your toilet. Push the flange into the hole until the flat base rests on the floor. Smear acrylonitrile-butadiene-styrene (ABS) glue on the bottom of the flange pipe and on the outside of the male 90 degree elbow joint end. Push the glued end of the elbow joint into the bottom of the flange and hold it in place for 30 seconds.
  2. Turn the female end of the articulation elbow to the existing sewer line (pipe). Connect the elbow joint to the existing sewer line by new two-inch drainage pipe and coupling connection as necessary, until you reach the existing sewer line. After cutting through the new sewer line, always remove all burrs with the dealer’s knife before gluing them. Also remember to glue both the end of the new sewer line and the inside of the coupling before connecting them together. When reaching the existing sewer line, cut the line (two parallel cuts for coupling with the two-inch pipe coming out of one side) and glue and install the coupling to the existing sewer line. Now glue and connect the new two-inch pipe for the new coupling.
  3. Close flat flange base to floor with 1 5/8-inch galvanized screws. The new sewer line is complete and the bathroom is ready to install.

Tips & Warnings

  • Drainage lines require a gradient of waste to travel down. Check with your permit office for the required gradient in your area. If the existing sewer line is much smaller than the elbow joint, you will not have to worry too much about this issue.
  • Always verify that the diameters of sewer pipes with your premises requires permit of office. However, two-inch drain pipes are generally used for toilets.
  • Sewer pipe couplings come in straight, 30, 45, 60 and 90 degree angles to help you install your sewer.
  • If you are using PVC sewer pipe and non-ABS pipe, you need first all the areas that need to be glued. Make sure the primer is dry before applying glue to the prepared areas.

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