What is the FIRST step in the rough-in of fixtures?

In the process of roughing in fixtures, determining the exact position of the opening for each fixture is crucial as the initial step. This step involves accurately marking where each plumbing fixture will be installed, including toilets, sinks, and other water-using appliances. Establishing these positions early on ensures that the plumbing lines can be laid out correctly and that there is adequate space for each fixture. It also allows for a coherent layout that adheres to building codes and design plans.

Once the specific positions are set, subsequent steps such as locating the main stack opening, determining trap positions, and finding sewer and water line locations can be performed more efficiently. The initial determination of fixture positions creates a foundational base for the entire plumbing system, ensuring that everything aligns with the intended design and functionality of the space.