My bathroom floor is tile over concrete. The house is settling and the slab has a few cracks so I understand why the toilet is no longer steady. Its shifting caused a leak in the water riser tube so I tightened the hold down bolts in an attempt to stabilize it and broke off a piece of the flange. Now that I've installed a flange repair kit, how can I tell how much I can tighten before cracking the toilet base?
I put the toilet back down without a wax ring to observe the gap. In the front I can use nickels for shims but in the back the gap is about
50% bigger than that. Is thinset mortar the best material to use to support the toilet all around the base? How do I force it under the base and how much is needed? Is it best to put some sort of coating on the floor and toilet so I can remove the mortar more easily next time I have to take off the toilet?