What’s the best way to check for toilet leaks?
Why is Your Toilet Leaking?
Toilet leaks can be wasteful and expensive. At least once a year, check your toilet for leaks by adding a small amount of red food coloring to the tank, and then check the toilet bowl in about 15 minutes.
If the toilet has not been flushed and the water in the toilet bowl is colored red (even slightly colored red or pink), then water is seeping through from the tank.