Here is a common toilet disaster and what to do about it:
The Toilet is Leaking
There are two situations in which the toilet could be leaking. The first is a situation where you hear water running and you do not actually see any water leaking out. This problem is likely coming from inside the tank. The fresh water coming into the toilet fills the tank up to get it ready for the next flush. It fills the tank and also puts a little water in the toilet bowl. When you hear the running it is because the rubber flapper inside the tank is not closing fully. Open the tank and see if the rubber flapper is closed down on the hole. If it is not, check to see if its chain is caught on something and straight it out so it will seat. If this does not work, you may need a new flapper. They are inexpensive and easy to find at any discount or hardware store. To install the new flapper, take the lid off the tank, turn off the water at the wall. Flush the toilet until all water is drained out of tank. Then take the old flapper off its hinges and chain and attach the new flapper. This should solve the problem of a running toilet.
The other situation in which the toilet could be leaking is if you actually see water on the floor. Dry up the water and toilet with a towel, and then look for more water to determine where it is coming from. If it is coming from the bottom of the tank that means the tank seals at the screws are leaking. These need to be replaced and cost only a few dollars. This part usually consists of a screw with a rubber gasket or washer, and when the rubber washer fails, it begins to leak. To replace these screws, again turn off the water at the wall. Then flush the toilet until the tank is empty. Unscrew old screws and remove, and then replace with new. Make sure tank is level both side-to-side and back-to-front. If the leak is not coming from the tank, it may be coming from the floor under the toilet base. This means that the wax ring that is between the floor and the toilet has failed and you need a new wax ring. Purchase a new wax ring for a few dollars at the hardware store. Be sure to buy a double-thick one if you think your tile is a bit high. The double-thick ones usually ensure no leaks in the future. To replace this, turn off the water at the wall. Flush the toilet until tank and bowl are empty. Pour a big bucket of water into the bowl to finish draining it. Then unscrew water lines. Then take caps off of screws on base of toilet (there are 2 of these), pop them off with a small screwdriver. You will see upside down screws with bolts. Now unscrew the bolt. Look at it to see how you will be putting it back together later. Next pull the entire toilet off of the floor. Get ready for some water spillage. The best thing to do is have a giant trash bag ready and place the base of the toilet into the trash bag to catch the water. Use a putty knife or spatula to scrape the old wax off of the base of the toilet and off of the floor. Get all of it cleaned off and wipe dry. Be sure to wear gloves for this step as the moisture here and the wax ring are dirty and possibly contaminated with waste material and carry diseases, so it is very important to wear gloves and wash your hands often. Next apply the new wax ring to the bottom of the toilet itself, pressing it firmly. Then place the entire toilet back on the floor, lining up the wax ring with the hole in the floor. Level the toilet and make sure it does not rock. You can buy small plastic wedges for this purpose, shove them under the toilet until it does not rock and later break them off so they do not show. Next bolt down the toilet, replace the caps over the screws. Reconnect the water lines; turn on water at all and do a test flush. Carefully examine all areas especially under the toilet base at the floor to check for leaks. Flush several times before actually using the toilet for waste water.