Start by checking for a toilet leak. Do this test at night or when you are out of the home for several hours. Color the water in the tank of the toilet with food coloring, coffee, cola etc. First thing in the morning or when you arrive home (before water is used) check the bowl of the toilet. If the color shows in the bowl, you have a toilet leak. Do this test to all of the toilets in the home.
If you do not find a problem with the toilets in your home, you may have a service line leak. Our customer service staff can send a service person out to take a meter reading to determine the amount of consumption that went through the meter since your bill was generated. If the service person determines a large amount of consumption, you may need to contact a plumber for further investigation of the problem.