Sinks must have waste outlets of a minimum diameter of what size?

The minimum diameter for waste outlets from sinks is established to ensure adequate drainage and prevent blockages. A diameter of 1 1/2 inches is specified because it allows for the proper flow of water and waste without creating excess pressure or risk of clogs that smaller diameters could cause. This size is large enough to accommodate the volume of water typical in sink usage while still being manageable for fittings and installations in various plumbing systems.

In cases where smaller diameters like 1 inch or 1 1/4 inches are considered, they do not provide sufficient drainage capabilities, especially for kitchen sinks that may deal with food waste or large quantities of water. Choosing a 2-inch outlet may not be necessary and could result in increased material costs and installation complexities without providing proportional benefits for typical sink applications. Thus, 1 1/2 inches strikes a balance between functionality, efficiency, and practicality as dictated by plumbing code requirements.