## 3 Background
### Traditional Design Method for DDWSSs  
The spatial and mechanical design of sanitary plumbing and drainage systems and components has not undergone substantial change in recent years [25]. CAD and 2D layouts are still suggested by standard regulations for the calculation methodology and required as the official presentation format [26]. At present, calculation methods must be guided by the specific codes and standards of the relevant country. The design, installation and specifications of plumbing systems in buildings are covered by guidelines [27]. Although standards specify equations, limits, considerations and minimum criteria, different hydraulic formulations have their respective justifications. In this context, RIDAA is currently the official code/regulation in Chilean practice. The conventional method for DDWSS design involves laborious work based on permanent user interaction with different professional software packages [6; 28]. Data manipulation and association comprise a highly manual process. These methods generally involve the following steps:  
* The design process starts with interpreting two-dimensional models (2D/CAD) and visualising and locating relevant data according to the potential input parameters presented in the project floor plan, such as types of plumbing fixtures, locations, quantities, rooms, equipment and other operational function requirements;
* Specialist sub-contractors use this information to develop their system routing, connecting elements of all building systems in compliance with architectural and structural designs [29]. Then, spreadsheets are commonly used to discretise data about piping systems, adding conditions and general project specifications that are not incorporated in the data extracted from the layout [6; 28];
* These spreadsheets, as shown in RIDAA's content, represent the official calculation and presentation formats. The system, material and geometric parameters of pipe paths are adjusted until an optimal solution is reached: the process is repeated until design parameters reach acceptable values according to the code ranges for pressure/flow rates and slopes in drinking water networks and drainage networks, respectively [26];
* Finally, contractors summarise and compile results, incorporating them into a two-dimensional model of the floor plans, elevations and isometrics, according to the symbology defined by the standards. This symbology is established for the water supply and sanitary treatment companies in the area, which are responsible for providing and maintaining connections with the public network. Urbanisation through residential projects involves integration of several engineering specialists. Contractors develop their models individually, following project requirements for optimal functionality. Therefore, they generally do not consider other systems from an interrelated viewpoint [29]. Coordination is needed to detect and eliminate spatial and functional interferences among systems; drawings for multiple layouts must be overlaid and compared [30]. In two-dimensional design, visualisation is limited, the data-sharing process easily comes into conflict with the work of other professionals and work lacks efficiency [31]. This repeatedly generates rework and coordination meetings, as re-routing systems and the relocation of elements are required to avoid clashes with a significantly