The decision of whether to install caulk around the base of a toilet is often a matter of personal choice, but it might also be a legal requirement, depending on the particular area you are in. The subject is often a matter of debate between both homeowners and toilet installers.
There are reasons when caulking the toilet may be advantageous.
The decision to the caulk a toilet may not be in your hands. The Uniform Plumbing Code, which applies to the installation and inspections of plumbing systems, says that where plumbing fixtures, such as a toilet, meet the floor, the joint must have a water-tight seal.
Whether this code is enforced may be a decision of local inspectors. If the home is a new construction, the responsibility for following this code requirement may fall on the builder.
For older homes, the responsibility is on the homeowner to follow the plumbing code.
One need for caulking a toilet base that arises out of concerns over cleanliness is if urine falls from toilet users onto the floor, which can seep underneath an uncaulked toilet base and cause a bothersome smell. Caulking the toilet base keeps urine from traveling beneath the toilet, and it can be more easily cleaned up before it collects and stinks.
Also, water from mopping the bathroom floor, or water that drips off persons exiting the bathtub or shower, may run beneath a toilet without caulking.
If the tile floor underneath the toilet is slightly uneven, the toilet may rock just a small amount when you sit on it. If the toilet rocks too much, the wax ring's seal underneath it will be compromised, leading to leaks of both water and sewer gases from between the toilet and the flange underneath it.
To counter this slight unevenness, apply caulk around the toilet base to reduce the toilet's potential to move and rock. An alternative to caulking in this case is installing shims to even out the toilet base.
Leak Detection Worries
Some homeowners may prefer that the toilet not be caulked, so that a leak from underneath the fixture can be noticed quicker. This leak is caused by a faulty wax gasket and will not go away until the gasket is replaced.
The leak can damage the floor and the sub-floor underneath the toilet. To avoid an unnoticed leak, you can caulk around the sides and front of the toilet base, and simply leave the back of the toilet without caulk.