How to Replace a Toilet in Concrete

Written by nathan mcginty
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How to Replace a Toilet in Concrete
Whether concrete is the floor or subfloor, replacing the toilet is straightforward. (Jupiterimages/ Images)

Concrete is most typically used as a subfloor, but is also a popular choice in lofts and apartments for that "urban" look and feel. Replacing a toilet mounted on concrete isn't any different than replacing a toilet mounted on any other type of surface. The main thing to remember is to clean off the flange area as much as possible before installing the new toilet. That way, you will have a tight seal between the toilet and the flange opening.

Skill level:
Moderately Easy

Things you need

  • Towel
  • Sponge
  • Adjustable wrench
  • Utility knife
  • Putty knife
  • Rag
  • Isopropyl alcohol
  • Wax ring
  • New toilet and hardware
  • Plumber's tape

Show MoreHide


    Remove the Old Toilet

  1. 1

    Shut off the water supply to the toilet. Look behind the toilet for the water supply valve. It is a small, metal valve connected to either the floor or wall. A hose leads from the valve into the toilet tank. Rotate the knob clockwise to shut off the water.

  2. 2

    Remove the toilet tank lid. Flush the tank and continue holding down the handle until the water inside has vacated. Sop up any remaining water with a rag and sponge.

  3. 3

    Unscrew the water supply hose or tube coupling from the tank's underside. Loosen the bolts on the bottom of the tank (two or three, depending on your model) and lift the tank off the back of the toilet.

  4. 4

    Remove the plastic caps on the bolts at the base of the toilet. Unscrew the bolts with an adjustable wrench.

  5. 5

    Run a sharp utility knife around the caulk at the base of the toilet, taking care not to scrape the concrete. Gently rock the toilet back and forth until it comes loose from the floor. Lift the toilet bowl up and off the floor.

    Install the New Toilet

  1. 1

    Clean off the area around the flange. Scrape away any old caulk with a putty knife. Clean up any wax residue with a rag soaked in isopropyl alcohol. Insert two new flange bolts, with the threads pointing upward, into the slots on the side of the flange.

  2. 2

    Turn the new toilet bowl over. Press the wax ring into place on the toilet's underside. Turn the toilet bowl right side up, taking care not to let the wax ring touch the floor. Manoeuvre the toilet into place over the flange. As you do, line up the wax ring and outlet in the bottom of the bowl with the flange opening. Slowly lower the toilet bowl into place over the flange. (Have an assistant help you if this is a heavy bowl.) Check that the flange bolts poke up through the holes in the base of the bowl.

  3. 3

    Insert the plastic and metal washers over the flange bolts. Thread the flange nuts above the washers. Hand tighten these bolts. Take the adjustable wrench and tighten each side, one turn at a time, until the bowl is secure.

  4. 4

    Place the tank on the back of the bowl. Insert the tank bolts through the bottom of the tank. Secure the bolts by threading the nuts on from the bottom.

  5. 5

    Wrap the inlet at the bottom of the tank with plumber's tape. Connect the water supply hose or coupling. Turn the knob counterclockwise to restore the water supply. Let the tank fill.

  6. 6

    Flush the toilet. Check for leaks. Tighten any bolts, if needed.

Tips and warnings

  • Use caution when tightening toilet bolts. Overtightening can crack the porcelain.

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