Abstract: Preventive maintenance to sewer lines is made more effective by using a predictive knowledge based assessment of those sewer lines most likely needing maintenance. Such predictive methods, are methodically applied to a sewer line system, to provide rodding to those sewer lines in need of maintenance or likely to need maintenance in the near future. Hence, non-problematic sewer lines are identified by default and are not unnecessarily serviced. Sewer lines are identified for preventive maintenance by identifying root intrusion, grease, and grit accumulation sources.