Every fixture drain must connect how to the waste stack?

The connection of every fixture drain to the waste stack must be done separately to ensure that each drain can function effectively without interference from others. This separate connection is necessary to maintain proper flow and prevent potential backflow issues. It allows for individual venting and drainage which minimizes the risk of clogs and ensures that the drainage system can accommodate the specific needs of each fixture.

Connecting fixture drains separately also aids in easier access for maintenance and troubleshooting, as problems can generally be isolated to one specific drain rather than affecting multiple fixtures in a collective connection scenario. Moreover, the plumbing code emphasizes the need for each fixture to have its own dedicated path to the waste stack to adhere to best practices for sanitation and efficiency in the plumbing system.