Illinois Plumbing Code Practice Exam 2026 – All-in-One Guide for Exam Success!

The minimum drain size for a kitchen sink is specified as 1½ inches in diameter according to the Illinois Plumbing Code. This size is determined based on several factors, including the volume of wastewater generated by the kitchen sink and the need to ensure effective drainage without risk of clogging.

Kitchen sinks typically handle significant amounts of water and food waste, so a larger drain diameter helps facilitate efficient drainage. A 1½ inch drain provides a balance between adequate flow and manageable installation requirements, ensuring that the sink can properly handle the typical waste load without backing up.

Smaller drain sizes, such as 1 inch or 1¼ inches, may lead to slower drainage and an increased likelihood of clogs, especially in a busy kitchen setting where water is used frequently. A 2-inch drain could be excessive for a standard kitchen sink, potentially complicating installation and increasing costs without delivering substantial benefits.

Understanding these specifications helps ensure proper installation and function in compliance with the plumbing code, promoting both efficiency and longevity of the plumbing system.