How to install a toilet on a concrete floor

Updated February 21, 2017

Toilets can be installed on a number of different floor surfaces, including concrete. When installing a toilet, the bowl is first connected to the metal flange opening in the floor, known as a closet flange. This flange holds a pair of T bolts that secure the toilet to the flange opening and also the floor. The main thing to be aware of when installing a toilet on a concrete floor is that the floor is smooth and clear of any obstructions. An even concrete floor can create a bad seal between the toilet, flange and the wax seal, resulting in water leakage.

Clean up the area of the concrete floor around the flange. Scrape up any old remnants of putty, wax rings or caulk with the putty knife. Sand down any rough spots in the concrete with a power sander. Vacuum up debris with a shop vacuum.

Insert the two flange bolts, threads up, into the closet flange. Press the wax ring into place around the flange opening.

Turn the toilet bowl over. Roll out a thin bead of plumber's putty and press it into place around the underside edge of the toilet bottom. Lift the toilet up and position it over the flange so that the outlet on the toilet aligns with the flange opening. At the same time, ensure that the flange bolts poke up through the holes in the base of the toilet. Lower the toilet once aligned and press into place on the ground.

Slip the plastic and metal washers over the flange bolts. Tighten the flange nuts by hand. Take the wrench and tighten one side by a turn, then do the other side. Repeat this process until the toilet is secure on the concrete floor.

Place the tank on the back of the toilet. Insert the tank bolts and washers into the bottom of the tank. Secure with the tank screws from underneath.

Wrap the inlet threads on the tank with plumber's tape. Connect the plastic coupling from the water supply hose to the tank inlet. Tighten with the wrench.

Turn on the water and allow the tank to fill. Flush the toilet and check for proper operation.


If the concrete floor is uneven, you can utilise toilet shims to bring the toilet level.


Do not overtighten any of the bolts, as this can crack the porcelain.

Things You'll Need

  • Toilet
  • Putty knife
  • Shop vac
  • Power sander
  • Plumber's putty
  • Wax ring
  • Wrench
  • Pliers
  • Plumber's tape
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About the Author

Nathan McGinty started writing in 1995. He has a Bachelor of Science in communications from the University of Texas at Austin and a Master of Arts in international journalism from City University, London. He has worked in the technology industry for more than 20 years, in positions ranging from tech support to marketing.