The most common cause of a leaking toilet is the flapper. This is the rubber part that releases water from the toilet tank into the bowl. Over time the rubber decays and can build up a layer of minerals. These factors affect its ability to create a water tight seal.
Checking for a leak and replacing a toilet flapper is a relatively easy, inexpensive do it yourself project for homeowners. One way to check for a toilet leak is to place a couple drops of food coloring into the toilet tank. Let the toilet sit without flushing for at least 15 minutes. If you see color show up in the bowl, you need to replace the toilet flapper.
The most common type of toilet flapper is a universal flap that hooks onto the overflow pipe in the center of the toilet tank. Villa Park Hardware suggests turning off the shut off valve to the toilet and bring the flapper to your local hardware store. There are a few different styles depending on the toilet.
The video below shows the most common style. They also show some other toilet flaps on their YouTube channel. You can visit the Villa Park Hardware at 46 S. Villa Ave. Villa Park, IL 60181.
You can view the steps at http://www.youtube.com/