I just had a new septic tank and leachfield installed. The contractor moved the main outlet (the big pipe that goes through the cellar wall) up. It now exits the cellar 2 feet higher than where it used to exit. 2 days later, I have an odor in the kitchen. I'm worried that, by moving the outlet, the contractor took the gravity out of the system within the house.

The large PVC pipe that runs across the cellar ceiling is fairly parallel to the cellar floor. It used to drop just before exiting; now it doesn't drop. Is this a problem?

If everything is properly trapped and the joints in the pipe sealed, you shouldn't have an odor problem with the new location of the pipe. I would complain to the contractor. Was the job inspected?