Toilets can leak for various reasons. For your reference, here is a toilet diagram:
Here are the typical reasons for toilet leaks, ultimately resulting in damage and a higher water bill:
Supply line leaking: The line that supplies water to your toilet could be damaged or loose. Water lines can be damaged if the rubber seal ring, also known as gasket, is corroded or split, or the line is not tightened enough on the threads, faulty installation, or faulty thread sealant.
Wax ring Leakage: The wax ring that seals the base of the toilet to the drainpipe could be worn out, broken or loose. Wax rings last for a very long time, only if a toilet is installed correctly with an evenly mounted toilet over the drain and wax ring. If this does not happen, wax rings will begin to let water seep through over time. For the readers information, this is also why you do not completely seal the bottom edge of the toilet to the floor all around, because you need see if it leaks on the floor as shown in the picture below.
Damaged closet flange: This flange is between the drainpipe and the wax ring seal. If this flange is rusted out or cracked, you will not be able to properly tighten the toilet and wax ring to the drain. The white ring on the floor is a closet flange in the picture below:
Loose flush valve: The valve that lets water into the bowl when you flush could be loose.
Loose connection where the tank meets the toilet: Check the connecting bolts. If they seem loose or you can see water gathering in that area, use the screwdriver to tighten them ( suggestion: use a wide flat head screwdriver).
Damaged or worn-out fill valve: If your fill valve is damaged or worn out, it can start to leak, which will cause water to constantly flow into the tank and eventually overflow into the toilet bowl.
These problems can cause water to drip or seep out from the base of the toilet or the tank. If left unaddressed, these leaks can cause extensive damage to the flooring and walls. The water from a toilet base is not clean to begin with, and the excess water can create a moist environment that promotes the growth of mold and mildew. Most of these issues can be resolved without professional assistance since the repairs are typically straightforward and inexpensive. However, if you’re unsure or apprehensive about repair jobs, never hesitate to contact a professional.