1.  Take a look at your water usage during a colder month, such as January or February.  If a family of four exceeds 12,000 gallons per month, there are serious leaks.

2.  Check your water meter before and after a two-hour period when no water is being used.  If the meter changes at all, you probably have a leak.

3.  Identify toilet leaks by placing a drop of food coloring in the toilet tank.  If any color shows up in the bowl after 10 minutes, you have a leak.  (Be sure to flush immediately after the experiment to avoid staining the tank.)

4.  Examine faucet gaskets and pipe fittings for any water on the outside of the pipe to check for surface leaks.