How to Install a Toilet on a Concrete Slab

Written by nathan mcginty
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How to Install a Toilet on a Concrete Slab
(Jupiterimages/ Images)

A concrete slab is a common foundation material in many parts of the U.S. Carpet, linoleum, tile or another material then covers the tile to make it more comfortable for walking. It's possible to install a toilet directly on a concrete slab. You would do this, for example, if you wanted to first install your toilet and then lay down a tile floor in your bathroom.

Skill level:
Moderately Easy

Things you need

  • Toilet
  • Wax ring
  • Flange bolts (2)
  • Plumber's putty
  • Wrench
  • Pliers
  • Tank bolts (2 or more)
  • Water supply hose
  • Plumber's tape

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  1. 1

    Clean off the concrete slab around the flange. Use the putty knife or paint scraper to remove any construction debris that might be adhering to the slab. Use the cleaner and rags to wipe up any mould or mildew that might be growing on the slab.

  2. 2

    Insert the flange bolts with the threads up into the flange. Press the wax ring into place around the flange opening.

  3. 3

    Turn the toilet bowl upside down. Roll out a bead of plumber's putty and press this into place around the underside of the rim. Turn the toilet right side up and lower it into place over the flange. Line up the outlet in the bottom of the bowl with the flange opening. While doing that, ensure that the bolts in the bottom poke up through the holes in the bottom of the toilet. Have an assistant help you if this is a heavy toilet.

  4. 4

    Slip the plastic and metal washers over the end of the bolts. Tighten the nuts onto the end of the bolts.

  5. 5

    Place the toilet on the back of the tank. Insert the tank bolts through the holes in the bottom of the tank. Tighten the nuts on the threads sticking through the bottom.

  6. 6

    Wrap the threads on the water supply valve on the wall behind the toilet and the inlet on the bottom of the tank with plumber's tape. Connect the plastic coupling on the underside of the tank and run it to the supply valve. Thread the metal coupling on the end of the supply line to the inlet.

  7. 7

    Open up the water supply valve and allow the tank to fill. Flush the toilet and check for leaks. Tighten any bolts if necessary.

Tips and warnings

  • Use pipe thread compound in place of plumber's tape, if desired.

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