Most common until 1940. Plastic 30-40 yrs. Concrete 20 yrs. Vitreous china 25-30 yrs. Plastic 50-70 yrs.
Useful life depends upon soil conditions.
Acid in soils can eat through plastic. Cast iron life Lead approx. Joints can deteriorate and cannot be patched. If bathroom is remodeled, lead must be replaced. Galvanized 50-70 yrs.