I installed new toilet and flange on concrete basement floor but on top of tile. The toilet rocks slightly front to back.

Did I maybe not get flange tight against tile? What might I check for?

I have no problem removing as it has not been used yet.

  • You can check if the floor is level by seeing if it "rocks" when not on the flange. Is the flange plastic or metal?
    – rogerdpack
    Jan 28, 2022 at 17:50
  • How long has it rocked? I just reinstalled one of mine after replacing the flooring and it rocked a little at first because the wax ring was too cold and didn't fully compress initially. After keeping weight on it for 10 min or so while reinstalling the plumbing connections and tacking trim back up, etc., it had fully seated and the base sat flat.
    – Chris O
    Jan 28, 2022 at 19:52

3 Answers 3


There are plastic wedges designed to stop rocking of toilets. Don't try to stop the rocking by tightening the floor bolts.


In my experience you won't get a dead-solid mount on a hard floor about 90% of the time. The toilet base and the tile are too likely to have imperfections that affect the connection.

So, rely on caulk. Clear, 100% pure silicone in a bead pressed into the void under the toilet will make it solid. I usually do the front and sides, but leave the back open. It's not necessary to do the back and it's a good place to leave a leak indication drain.

If you don't trust your caulking skills, mask the floor directly under the outer edge of the toilet base (or slightly inside). Inject the caulk in small beads and work it into a cove with your finger. Add more only if it presses in too far.

Give it a few hours to fully cure and be happy.


I used to remodel a lot of bathrooms. As long as the flooring at the base of the toilet is sound, I second the use of plastic shims to level it and then caulk the base. That's the best solution

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