What is the code's term for the point where a water softener backwash drain discharges above the flood level rim of a floor drain?

The term that describes the point where a water softener backwash drain discharges above the flood level rim of a floor drain is indeed referred to as an air gap. An air gap is a critical feature in plumbing systems that prevents backflow by creating a physical separation between the end of a discharge pipe and the water surface in a receiving basin or drain.

This separation ensures that contaminants, such as those that might be present in the backwash from a water softener, cannot siphon back into the potable water supply. Maintaining this air gap is essential for protecting public health and ensuring safe water consumption. It acts as a safeguard against potential cross-connections that may occur if the drainage system experiences pressure changes, thereby allowing non-potable water to enter the clean water system.

The other terms mentioned do not accurately describe this specific plumbing scenario, further establishing the uniqueness of the term "air gap" in this context.