Given several plumbing fixtures, what is the minimum size allowed for the building drain according to the code?

The minimum size allowed for a building drain, as per plumbing code standards, is 2 inches. This dimension is established to ensure that the building drain can adequately handle the expected volume of wastewater and potential solids from the plumbing fixtures within the building. A minimum diameter of 2 inches allows for sufficient flow capacity, reducing the risk of clogs and promoting effective drainage.

In addition, this size takes into consideration factors such as the number of fixtures and the type of waste being discharged. Smaller diameters, such as 1 inch or 1.5 inches, would not provide adequate drainage for the majority of residential plumbing applications, potentially leading to functional issues over time. A 2.5-inch size is typically more than necessary for a standard residential setting, potentially leading to increased costs and complexity where it is not required. Therefore, the code specifies 2 inches as the minimum effective size for ensuring proper drainage in residential plumbing systems.