How many fixtures can be discharged onto a stack above a stack vented water closet?

The correct response, which indicates that four fixtures can be discharged onto a stack above a stack-vented water closet, aligns with the plumbing code's guidelines regarding drainage systems and venting. In plumbing systems, stack-vented water closets are designed to effectively manage wastewater and ensure proper venting to prevent issues such as negative pressure or siphoning.

The capacity to discharge up to four fixtures above a stack-vented water closet is a specific requirement that allows for adequate drainage without risking the performance of the plumbing system. This limit ensures that the stack can handle the additional flow and that the venting remains effective, controlling odors and maintaining air pressure within the drainage system.

Thus, adherences to these specifications in the plumbing code are crucial for ensuring that waste is properly managed, preventing clogs or backups, and maintaining a safe and functional plumbing environment.