If water pools around the base of your toilet, one of the toilet's seals may be leaking. But if you live in a warm, humid climate, check to see if the tank is sweating before you make other repairs. In humid climates, warm room air can condense on the cooler surfaces of a toilet and drip onto the floor. This encourages mold and, over time, can rot the subflooring. The cold porcelain tank is the problem--it never warms up because, whenever the toilet is flushed, it refills with cold water. When moisture-laden warm air contacts the cold surfaces of the tank, it condenses and "sweats." Moisture collects and drips down the tank to the floor.
The simplest solution for a sweating toilet is to insulate it with a foam toilet tank liner, made to be glued on the tank's inner surfaces. Toilet tank liners are available in home improvement centers and online. Empty the water by turning off the supply valve at the wall and flushing the toilet. Wipe down the inner walls of the tank. Cut the insulation panels to fit and attach them according to the label directions.
For a more thorough and permanent solution, you can talk to a plumber about installing a tempering valve on the cold water line that supplies the toilet. This draws a little hot water from a hot water pipe and mixes it with the cold water entering the toilet tank to raise the tank's temperature. Be advised that this solution will also use more energy because the water heater will need to warm the water.
If it appears that the tank is not sweating but water still pools around the toilet's base, see How to Repair a Toilet That Leaks at the Base.
