In order to repair a toilet leak, first take the time to carefully assess the situation so you ensure you address the cause of the problem. An external toilet leak is usually a messy and relatively urgent problem.
If left unattended, such a leak can have a number of undesirable consequences such as water on your floor, floor damage, odors, and/or wasted water. Thus, you should either repair it yourself or call a qualified professional plumber.
External toilet leaks are typically either from the base of the toilet at floor level or from the middle, back of the fixture at tank level. To find the leak, get a flashlight and carefully try to determine its source. If there is no water dripping above floor level and the leak seems to get worse when you flush, the problem is likely related to the seal between the base of toilet and the floor flange.
In contrast, if you do find water dripping from the back of the toilet at about seat level, the problem is likely related to a faulty seal between the tank and the bowl. In either case, you need to turn off the water to the toilet at the water valve and flush the toilet to empty the tank.
To attempt to repair a toilet leak at the base, first just snug up (do not over tighten) the bolts holding the toilet to the flange. Refill the toilet and see if the leak goes away. If it doesn’t, disconnect and re-empty the toilet; un-bolt the toilet from the floor, disconnect the water line from the tank, and rock the toilet off the flange.
Inspect the flange and floor. If either appears damaged, call a professional plumber. If they appear in good order, go to any hardware store and purchase a new quality wax ring. Remove the old wax ring, and replace it on the flange. Re-install the toilet, re-connect, and test.
To attempt to repair a toilet leak from the tank, first snug up (do not over tighten) the tank bolts in the bottom of the tank. Then refill the toilet and see if the leak goes away. If it doesn’t, disconnect and re-empty the toilet; un-bolt the tank from the toilet base, inspect the rubber washers on the bolts and the tank-to-bowl gasket.
If either appears worn or damaged, a larger home improvement store or plumbing supply store may stock these parts. Purchase new ones, re-assemble, and test toilet. Obviously if you can’t find the parts, or still have a leak, it is time to either replace the entire toilet, or call a professional plumber.