We recently received a call from a residential customer who had reveived a very high gas bill.  He assumed it was a gas leak, and we sent a technician to evaluate the problem.  The tech discovered that the water heater was running constantly, indicating a plumbing leak somewhere within the house.  We then scheduled a leak locator to go to the customer's house and determine the exact location of the leak so we could give an estimate for the repair.  It pays to be aware of your regular costs.  When you see a bill come through that seems higher than normal, it's always best to have a professional out to investigate the problem.