If only one drain is backing up, it's typically related to plumbing issues, unless that particular drain is the one closest to the septic system. To discern the cause, when the closest drain to the septic system becomes clogged, we suggest running water in the next closest drain. If the next closest drain also backs up, then you'll need a septic company. If it drains properly, you should call a plumber. It's worth noting that when a septic issue causes plumbing backups, it usually affects more than one drain.
