"Plumbing system" means all potable water supply and distribution pipes, all plumbing fixtures and traps, all drainage and vent pipes, and all building drains and appurtenances within the property lines of the premises except: a) fixed lawn sprinkler systems beyond backflow prevention devices, and b) building sewers and private wastewater disposal systems three feet (3') or more beyond the outside walls of buildings. Included also are potable water treating or using equipment and water heaters. (Prior code § 5-14-2)