Your property's source and drainage procedure have to usually be two distinctive subsystems, with no overlapping. Within the fixtures (bridges concerning The 2 systems), the air admitted with the vent stack and vent pipes keeps the traps sealed and prevents sewer gases from backing up with the drains. See https://1701-b.s3-ap-northeast-1.amazonaws.com/streamline-plumbing-solutions/PlumbingandDrainage.html