Several things could be causing the wobble. The closet bolts might not be tight, or the closet flange may be broken or bent. Also, the wax ring that seals the connection between the toilet and the discharge pipe may be not be set properly.
Tightening the closet bolts is an easy fix. Installing a new wax ring is a bit tougher. Repairing the closet flange is more difficult, but it can be done. In any case, fix the wobble before it becomes a leak.
The standard household commode discharges into a 3- or 4-inch waste line called a closet bend. We don’t know the origin of this name, but it may come from water closet, a name for a bathroom. The closet bend is screwed or bolted to the floor by a flange – the closet flange.
A wax ring is placed on the bottom of the toilet where it discharges into the closet bend. The wax ring has two purposes. It creates a watertight seal at the joint where the toilet discharges into the closet bend. It also acts as a gasket to take up slack in what might be an uneven floor.
The porcelain commode is secured to the closet flange by two bolts with nuts attached to the closet flange. Flat perpendicular metal pieces are welded to the bottom of each bolt. These insert into slots in the flange. When the toilet is placed over the bolts and tightened down, they provide a solid connection to the flange and the floor.
We’ve installed many retrofit tile bathroom floors. Each time we’ve had to take up the toilet and either replace it or reset it. We’ve always found that a tile installation required that a second wax ring be installed to get a firmly set commode.
If you didn’t set the toilet with two wax rings, we suggest you take up the toilet and do so. It’s good insurance against a leak. It will also give you the opportunity to make sure the closet bolts are snug and allow you to check the closet flange to make sure it is secure.
To remove the toilet, turn the water off, detach the supply line and drain the toilet. Next, unscrew the closet bolts and carefully lift the toilet off the closet flange.
Once the toilet is clear, clean the old wax ring off the bottom of the toilet. Inspect the closet flange to determine if it is bent or broken. If it’s made of cast iron and broken, the local plumbing supply house should stock a repair kit. This is a specialty item generally not available at home centers or hardware stores.
Once the flange is sound, place two wax rings on the bottom of the commode at the place the closet bolts in the flange. Gently and carefully set the toilet in place, making sure that the discharge of the toilet is directly over the closet flange and that the closet bolts protrude from the holes in the bottom of the toilet.
Use new bolts. Don’t try to save money by trying to use the old ones – they’ll be too short. Press the toilet down to get a firm seal at the wax ring. Snug the nuts down on the closet bolts using the washers provided. There should be a metal washer and a plastic washer for each bolt. Metal first, then plastic. Don’t overtighten the nut; you run the risk of cracking the commode. Been there, done that, not good.
Finally, apply a bead of tub and tile caulk around the base of the toilet, leaving a gap at the rear so that if the toilet leaks at some time, the water has a place to go.