How to Install Toilet Shims

Updated February 21, 2017

A wobbling toilet can start as a minor annoyance, but soon can develop into a major problem. The toilet is connected to the floor by bolts on the closet flange, where the sewage exits. Between these two is a wax ring used to keep in water and sewer gases. A toilet that rocks back and forth can damage this wax ring over time, causing water leakage. Fix a rocky toilet by installing toilet shims--normally short (2- to 3-inch) plastic inserts. If you can't find plastic shims, standard wooden shims will work just as well.

Cut away any caulk at the base of your toilet with a sharp utility knife.

Loosen the flange bolts at the base of your toilet. These are usually covered by plastic caps. Undo the screws two or three turns with the wrench.

Insert the shims underneath the toilet bowl where it is uneven. Use a level sitting on top of the tank to determine which way the toilet is leaning. Two or more shims may be necessary.

Tighten the flange bolts down once the toilet is level. Tighten them hand tight to start, then one more turn with the wrench.

Sit on the toilet to make sure it's no longer wobbling.

Cut off any excess part of the shim(s) sticking out from underneath the bowl with the utility knife.

Caulk around the base of the toilet.


Do not over-tighten the flange bolts--doing so can crack the porcelain.

Things You'll Need

  • Toilet shims
  • Utility knife
  • Wrench
  • Level
  • Caulk
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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.