Use Food Coloring to Diagnose a Leaking Toilet
If you have a heavy leak in your toilet, it's easy to diagnose - the faint sound of the toilet tank constantly replenishing is a dead give away. What about a slow leak? Diagnose it with food coloring.
If you have a slow leak in your toilet tank, hundreds of gallons are just slowly and silently cascading down the side of your toilet bowl every month. Fortunately you can easily detect if the uptick in you water bill is from a slow leak or not.
A simple test for toilet water leaks, place a half a dozen or so drops of food coloring into the toilet tank. Leave the toilet alone for a half hour or more. Come back and check to see if the water in the bowl of the toilet has become tinted with the food-coloring dye from the tank. If it has, you've got a leak between the tank and the bowl.