Check for leaks in toilet water feed and tank bottom.
9 out of 10 complaints that local water utilities receive from homeowners can be traced back to leaky toilets. You can do your own quick and easy test if you suspect a leaky loo. First, take the top off your tank and put a few drops of food coloring in the water. Wait at least 30 minutes and if you see ANY color in your bowl after that time, you’ve sprung a leak somewhere and it’s time to call a plumber.