How to Install a Toilet Flange on a Concrete Floor

Written by james werning
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How to Install a Toilet Flange on a Concrete Floor
Keep reminding yourself how good it will look when you are done. (disables bathroom image by Wolszczak from

Maybe you've decided to install a bathroom in the basement. It's an enormous job, especially considering the fact that you have to run the PVC sewer pipes through the concrete slab to where the toilet will stand. Once that is completed, it will take some careful planning to get the toilet mounted correctly on top of the concrete floor. Thankfully it won't take much in terms of time or expense. However, you have to be careful where you place the toilet, because you don't want to move it once you're done with the job.

Skill level:

Things you need

  • Jackhammer or hammer and cold chisel
  • 4-inch PVC pipe
  • 4-inch PVC coupling
  • Hacksaw
  • PVC primer
  • PVC cement
  • 4- by 2-inch PVC toilet flange
  • Duct tape
  • Concrete
  • 2 toilet mounting bolts
  • Trowel

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  1. 1

    Determine exactly where the flange will be located, and break away any concrete obstructions. Install PVC pipe and couplings to terminate vertically 1.5 inches below the concrete floor surface. Adjust this height if necessary so that the top surface of the toilet flange will be 0.5 inches above the finished floor surface.

  2. 2

    Glue a 4- by 2-inch PVC toilet flange to the top of the 4-inch pipe, positioning it so that the mounting bolt holes are positioned at 3- and 9-o'clock to the toilet. Tape the hole in the top of the flange shut with duct tape (to keep concrete out). Inspect all subfloor pipe joints.

  3. 3

    Pour concrete around the flange, filling all gaps and smoothing the surface. Place the toilet mounting bolts into the flange holes while the concrete is wet. Allow to dry overnight. Remove the duct tape. Mount the toilet.

Tips and warnings

  • A 4- by 2-inch PVC toilet flange will fit on 4-inch PVC pipe. Choose the correct size to fit your sewer pipes.

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