In all buildings hereafter erected, both public and private, and in all buildings already built or erected wherein any plumbing is installed or wherein any sewer connected pipe shall be repaired or changed, except for minor repairs, on the sewer side of the trap, the drain, the soil, rainwater and other pipe or pipes connected directly or indirectly to any drain, soil or waste pipe, and all traps, shall be exposed to view for inspection and test by the building inspector and shall not be covered until such test is made. (1990 Code § 14.301)