If water pools around the base of your toilet—especially during or immediately following a flush, the cause is usually a failed wax ring between the toilet’s base and the closet flange (waste pipe).
Replacing this ring involves pulling the toilet, so be sure the water is not coming from a leaking toilet tank or water-supply connection before you go to the trouble of replacing the wax ring.
First check for condensation on the surface (sweating). For more about this, see How to Fix a Toilet That Sweats.
Next, look for cracks in the tank and bowl. If either the toilet tank or bowl are cracked, replace the entire toilet. For information on how to do this, see How to Install a Toilet.
Use a rag to dry the floor around the toilet’s base. Lay a newspaper beneath the toilet’s tank, wait a few minutes, and check it for drips. If there is no sign of leaking but the water reappears around the base, the wax ring is probably the culprit. If drips appear, check the fittings directly above them for leaks.
When you buy a wax ring replacement, make sure to choose one with a rubber collar, which is less likely to leak in the future.
The process of replacing the wax ring is detailed in step-by-step captioned photographs in How to Install a Toilet.
