Check the toilet for leaks by removing the top off the tank and listening very closely. If you hear any hissing at all, try to locate where it is coming from. If you locate the area where the leak is coming from, assess it and determine if you can fix it. If you can't, then call a plumber.
- If nothing is noticeable, add some food colouring and put a couple of drops in the tank (not the bowl). Wait several minutes (don't flush) and if you have coloring in the bowl, you have a leak in the flapper at the bottom of the tank that is allowing water to seep through. At this point you can assess it if you want to do the repair yourself, or call a plumber.
- If you have more toilets, go ahead and repeat the process with each toilet to make sure you don't have more than one problem.