Short answer
Orangeburg is a bituminized fiber sewer pipe manufactured between 1945 and 1972, made of wood pulp impregnated with coal tar pitch. It softens, deforms, and collapses with age — most installations are now past the end of service life.
Long answer
Inspectors identify Orangeburg by camera scope. Visual cues: oval deformation, blistering, delamination of interior layers. Even functional Orangeburg is at end of life and represents a major finding in pre-purchase sewer scopes. Replacement is the durable fix; spot repairs are temporary. Typical replacement cost $8,000–$20,000 depending on length and depth.