Think you have a leaking toilet, try this simple dye test; it’s easy to do, it’s fast and it’s inexpensive.
First, carefully remove the toilet tank cover, it is breakable and sometimes impossible to match if you happen to break it. Lay it on a towel or wrap it in newspapers or a small old carpet.
Second, put several drops of food coloring into the water tank above the toilet (not in the toilet bowl :)), be sure to put enough dye into the tank that you can see the color change in the tank.
Third, wait 15 minutes WITHOUT flushing the toilet. After 15 minutes, if the toilet bowl water is the same color as the tank water, you can assume you have a leak.
If there is a leaking toilet, more than likely you can fix it by replacing the flapper valve, an inexpensive toilet repair you can probably do yourself.
This simple test works great and it saves money by stopping the costly water leaking into your toilet.