Pro Plumbers

If nothing inside the home was altered you should not be getting a smell. Personally I'm confused as to why the repair person would have left the original line there and ran another one through a new hole. I would have pulled the old line up, ran the new line (in PVC) and used the same hole in the septic tank instead of creating a new one. Did he seal up the hole in the tank from the old line?
The word "plumber" dates from the Roman Empire.[3] The Latin for lead is plumbum. Roman roofs used lead in conduits and drain pipes[4] and some were also covered with lead, lead was also used for piping and for making baths.[5] In medieval times anyone who worked with lead was referred to as a plumber as can be seen from an extract of workmen fixing a roof in Westminster Palace and were referred to as plumbers "To Gilbert de Westminster, plumber, working about the roof of the pantry of the little hall, covering it with lead, and about various defects in the roof of the little hall".[6] Thus a person with expertise in working with lead was first known as a Plumbarius which was later shortened to plumber.