Master Plumber Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

For a kitchen sink, the minimum size for the trap and trap arm is indeed 1-1/2 inches. This is based on standard plumbing codes which dictate the required dimensions for proper drainage and to effectively handle waste water from kitchen sinks.

A 1-1/2 inch trap allows for adequate flow and minimizes the risk of clogs that could occur if a smaller size were used. It's also worth noting that using the appropriate diameter helps maintain proper venting and pressure balance within the plumbing system, which prevents issues such as siphoning of the trap and allows for efficient drainage.

Other sizes, such as 2 inches or larger, are typically used for more substantial drainage needs or in larger plumbing systems, but for standard kitchen sink installations, 1-1/2 inches is recognized as the standard minimum to ensure compliance with plumbing codes and to promote optimal performance.