Toilets may need to be replaced for worn out circumstances or removed and replaced for remodeling purposes.  Toilet fixtures – like the flush kit, tank plug, and float will wear out within an number of years.  Sometimes clogs or repairs require the toilet to be removed from the floor for repairs.  Any type of toilet leak can lead to some serious flooding problems.  Similarly, your toilet may need to be replaced if you smell sewer gas in your bathroom, as inhaling this can be hazardous to your health, not to mention that the gases are flammable and pose a risk of fire and significantly property damage.  

Sometimes the wax beneath your toilet will dry out over time, and any movement of the fixture can cause it to crack, ruining the seal.  If the mounting bolts and nuts come loose and your toilet shifts or rocks, this is a good sign that your toilet – or at least the wax ring and flange below will need to be replaced.