Here’s how you can test your own toilet for leakage! (By the way, this won’t work for flush-mate air-assist style toilets!)
Please wear gloves, open the tank lid of the toilet, apply 3 to 4 drops of your choice of food coloring and let the toilet sit for 20 minutes. Return and take a look at the toilet bowl water. If any of your food coloring water from the tank is in the toilet, that means your experiencing a leak with your flush system, which may result in higher than normal water bills (it doesn’t take much of a leak to cost lots of money!).