How to Shim a Toilet Bowl

Updated April 17, 2017

A common problem that occurs in toilet installation is wobbling, or an uneven seal, which can lead to damaging and costly leaks. The best implements designed to correct this problem are toilet shims, tiny wedges that brace between the toilet's base and the floor to counteract imbalances between the surface and the toilet itself. The installation of shims can be a tricky prospect, combining the heavy force of a porcelain toilet with the fine-tuned touch of perfect balancing.

Locate the position of the wobbling in your toilet by pressing down firmly on various points around the rim of the bowl. Take note of any location where pressure causes the opposite side of the toilet to rise off the ground. Pay special attention to the front of the toilet, where pressure can often cause the rear of the toilet to rise.

Insert a shim in between the floor and the toilet's base near the point where it rises off the ground. Push it into the gap until it fills the aperture. Remove the shim and break the pointed end off so it does not protrude too far beneath the toilet, and then reinsert the shim.

Wobble the toilet back and forth. The looseness will be lessened to a wobble as the toilet moves on its new axis from pressure point to shim. Insert a second shim on the other side of the gap, near to the first shim. This will create a steady triangular base. For all except the most uneven floors, two shims will be sufficient to brace the toilet.

Remove the washers and nuts, lift the toilet off of the securing bolts and place the wax ring down where the toilet's base will rest on top of it. Be sure not to move any of the shims you have just placed. This ring will provide final stability. Replace the toilet and resecure it.

If desired, caulk around the base of the toilet. This is just a cosmetic choice -- the danger of leaks is not at the crease there, but rather in an unstable bowl causing the pipes to move. As long as the toilet is properly shimmed, there is no advantage to caulking or sealing the base beyond aesthetics.

Things You'll Need

  • Shims
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About the Author

Joe White has been writing since 2007. His work has appeared in various online publications, such as eHow and He graduated from the University of Dallas with a Bachelor of Arts in English.