Final answer:
The minimum size for hanger rods for pipes up to 4 inches in diameter is typically 3/8-inch, but it's important to check local building codes or consult with a structural engineer for specific requirements.
Step-by-step explanation:
The minimum size hanger rods required for supporting a pipe with a diameter up to 4 inches can vary based on several factors, including the weight of the pipe, the contents it carries, and building code requirements.
Generally, common practice and various building codes would suggest using a hanger rod with a diameter of at least 3/8-inch.
However, for precise specifications, it's best to consult the current local building codes or a professional structural engineer as requirements can differ based on the site-specific conditions and the loads involved.