If the leak seems to have started suddenly, it could be that the gasket has come loose and is leaking.
The most common reason for a leaky toilet is the flexible rubber ring that separates the valve and tank has deteriorated over time and sprung a leak, exposing the valve. This can happen quickly or gradually as the ring fails over time.
To repair this kind of leak, turn off the water at the shutoff valve under your sink. Remove the tank lid and lift out the old, worn rubber gasket. Clean all remnants of the old ring from the flange and valve seat. If necessary use a utility knife to scrape out deposits so they won't interfere with the seating of the new ring.
If you can't find the exact match, take an old ring to the hardware store with you and get a close match or just purchase a generic replacement. You don't need any special tools or connectors for the rubber ring but if your valve flange is corroded in place, you may need to remove the old valve with a screwdriver before installing a new one.
The process of fixing plumbing problems by yourself will demand time and patience. Plumbing problems should be fixed by a professional.If the leak seems to have started suddenly, it could be that the gasket has come loose and is leaking. It may also be that the flange (the metal or plastic part on which the toilet bowl sits) is cracked or corroded, allowing water beneath your toilet. Another possibility is that the wax ring, the soft washer that closes off the bottom of your toilet and provides sealing for the drainpipe, has failed. When the toilet is flushed, the water rises above the level of the ring and leaks around the base of the pipe.
If you suspect a leak at or near your toilet's flange, or your water flow is extremely low, turn off the supply and remove the toilet tank lid (either from under your sink or behind your toilet) to expose the valve assembly. If you see signs that liquid has seeped beneath your toilet, replace any worn washers or deteriorated flanges before reassembling things -- and call in a plumber if you're not sure what to do.Another toilet leaking issue can be due to tee bolts (t bolts), issue at the base of your toilet (base of the toilet do have unnoticeable toilet leaks), problem in the water supply line or water supply tube, the issue with the bolts (tee bolts and others), and more. Common problems can be with the water valve, drain flange, caps, drain the opening, tank, and more.
You'll need proper tools first. Keep a garbage bag, paper towels and terry cloth (microfibre towels) handy. Have putty knife, tee bolts, and other common toilet parts ready.
Disconnect the water supply. Empty the toilet tank. Remember this'll be a plumbing repairs fixture job.
If your water bills are high, perhaps more than having regular long showers, the problem can be with the tee bolts causing leaking toilet. Depending upon where the leak is coming from, there are various ways to fix a toilet and stop the leak. If you have running water in your bowl and it runs constantly, or if your toilet overflows after each flush, you will need to replace those parts of your toilet.If the leak is coming from beneath the toilet tank or near your toilet base, and water is leaking out on both sides of the base you probably have a ring issue. This can result when people try to "fix" their leaky toilets by themselves because they do not know how to replace a wax ring correctly. Wax rings may go bad over time and they can become damaged rather easily as well.
To ensure toilet leak at the base of your toilet is fixed, reconnect the water supply line and flush the toilet. When you flush the toilet, if there's no sign of water on the floor, then the base of the toilet is resolved. If not, then you'll need a plumber for sure.
Next, check the tee bolts that fasten the toilet to the floor. If the bolts are causing problems, you'll notice water on the floor. The floor must be dry even after flushing. If not, then first dry the floor with the towel. Once the floor is dry and the bolts have been replaced, we need to check if the bolts are working fine. Ensure bolts are not damaged. Also ensure that bolts are not rusty.
The wax ring is a type of sealant ring that sits at the bottom of the toilet and provides a sealing for the drain pipe. They work by trapping a small amount of water in the space between it and the toilet. The trapped water creates enough pressure to keep the seal intact and prevent leaks from occurring. If your toilet is leaking around the base, you likely need to replace or "re-bed" your wax ring correctly. Replacing a wax ring is something that anyone can do at home, but there are some things you should know about this repair project first. The wax ring can go bad over time, but it can also become damaged rather easily as well. It is common for plumbers to see leaky wax rings on toilets in older homes.
The sealing consists of two parts: one inside the drainpipe (where it meets up with your toilet) and one outside the drainpipe (where it meets up with the sewer).
The outside piece is the one that is most likely to leak. The toilet sealing leaks because, over time, minerals in the liquid will build up on the inside of this piece giving it a "whitish" colour. This build-up eventually can crack and/or completely envelop this part called the packing nut or rim gasket. This is the part that is now leaking and needs to be replaced. You may need to re-waterproof the base, similar to waterproofing a shower.The first thing you will need to do when you go to replace this toilet sealing is shut off your supply so no more liquid can flow into the drainpipe while you are working on it. There is a rubber gasket that sits between the packing nut and the outside of your toilet bowl.
This rubber gasket (also known as an "O-ring" seal), may no longer provide a waterproof seal and if this rubber gasket is worn, you need to replace both the packing nut and the rubber gasket at the same time.