Final answer:
The typical size of an air gap should be 2 inches, or twice the diameter of the supply pipe, and not less than 1 inch according to plumbing codes.
Step-by-step explanation:
The size of an air gap in plumbing refers to the space between the end of a water supply outlet and the flood-level rim of a receiving vessel, such as a sink, to prevent contaminated water from back flowing into the potable water system. According to the Uniform Plumbing Code (UPC) and the International Plumbing Code (IPC), the minimum required size of an air gap should be either 1 inch or twice the diameter of the supply pipe, whichever is greater, but not less than 1 inch
Therefore, the correct answer is typically B) 2 inches, assuming the supply pipe diameter is less than 1 inch. However, for certain equipment or under different plumbing codes, the requirements may vary.