What is the drain size required for a kitchen sink?

The required drain size for a kitchen sink is 1 1/2 inches. This size is specified in plumbing codes and standards because it provides adequate drainage capacity for the waste that a kitchen sink typically handles. Kitchen sinks commonly deal with greases, food particles, and liquids, which require a larger drain opening to prevent clogging and ensure efficient drainage. A 1 1/2-inch drain is designed to handle the volume of water and waste produced during kitchen activities, reducing the risk of backups and allowing for smooth drainage.

While smaller drain sizes, like 1 1/4 inches, might be suitable for other fixtures such as lavatory sinks, they do not provide the necessary flow rate needed for kitchen sinks. Larger options, such as 2 inches or 3 inches, are typically used in different plumbing contexts, such as for larger fixtures or main waste lines, and would not be appropriate for the specific application of a standard kitchen sink drain.