Continuing the discussion from Student Discussion: The 2021 International Residential Code® (IRC®) Exam Study Course:
What is the minimum required diameter for fixture tail pieces serving sinks, dishwashers, laundry tubs, bathtubs, and similar fixtures? For bidets, lavatories, and similar fixtures
The minimum required diameter for fixture tailpieces varies depending on the type of fixture. For sinks, dishwashers, laundry tubs, bathtubs, and similar fixtures, the minimum diameter is typically 1 1/2 inches. For bidets, lavatories, and similar fixtures, the minimum diameter is generally 1 1/4 inches. These requirements are based on standard plumbing codes, such as the International Plumbing Code (IPC) or Uniform Plumbing Code (UPC), though it is essential to verify specific requirements with the local plumbing code applicable to your region.