A water closet must be on a minimum of what size soil or waste pipe?

A water closet, or toilet, requires a minimum size of 3 inches for its soil or waste pipe to ensure proper drainage and to accommodate the volume of waste and water that it generates. The larger diameter helps prevent clogs and allows for adequate flow of both liquids and solids, which is crucial for maintaining hygiene and effective waste removal. Smaller diameters would increase the risk of blockages and reduce the overall efficiency of the plumbing system. Hence, 3 inches is established as the standard minimum size for soil pipes serving a water closet, ensuring that it can effectively handle the necessary waste disposal without issues.