Water-saving facilities were constructed in response to the sustainability and global issues all over the world. However, the performance of drainage systems must be ensured as the volume of flush water is reduced. Otherwise, it might cause sanitary problems to indoor environments and interrupt building functions. According to the methodology of investigation and observation, this paper categorized parameters that dominate the solid transportation performance of main drains. An empirical experiment was executed to clarify the quantitative influence of these parameters. A calculation model for estimating the boundary condition of main drain design is conducted. Furthermore, an estimation interface is validated and proposed as an assessment tool for practical application.

Practical implication: This paper offers an evaluation tool by statistic methodology to ensure solid transportation performance. An estimating model and regulation proposal of solid transportation in main drains of buildings that can guide the designer and engineer to confirm the performance of drainage system is validated and proved to be practicable. Furthermore, this research conducted an estimation interface to validate the solid transportation performance, which can offer an assessment tool for practical application. The results can contribute to building code guidelines and lead to new technical development of building drainage systems.