What is the minimum size of a trap for a kitchen sink?

The minimum size of a trap for a kitchen sink is 1.5 inches. This size is typically required because kitchen sinks often handle a significant amount of water and food waste. A trap that is 1.5 inches in diameter provides adequate flow capacity to efficiently handle the discharge from the sink, preventing clogs and ensuring proper drainage.

Additionally, the 1.5-inch size is significant as it aligns with standard plumbing practices that aim to maintain effective drainage and ventilation within the plumbing system, avoiding issues that can arise from smaller traps, such as slow drainage or backup problems. The standard also takes into account the volume of waste generated from typical kitchen activities, making this size the most practical choice for residential settings.