I here this all the time. What should you do? First thing to do is find your water meter. Water meters are usually out at the curb in front of your home or sometimes in the back adjacent to the alley way. This is an important thing to know about your home. What you want to do is open the meter box and look at the dial on your meter. There is a small red triangle on the meter and this triangle measures small increments of water flow. Mark this little triangle with a sharpie and stop using water in the house. Return after a few minutes and check to see if the red triangle has spun, this will tell you if there is a leak somewhere in your system. Happy Hunting!