Illinois Plumbing Code Practice

The appropriate discharge method for wash water and rinse water drain lines from water treatment units is through a vertical air gap. This choice is correct because an air gap serves as a vital backflow prevention mechanism, ensuring that contaminated water from treatment processes does not siphon back into the potable water supply. The air gap creates a physical separation that meets public health standards and prevents any potential cross-connection between the treated waste and clean water systems.

In contrast, discharging through a floor drain could pose a risk of contamination, while a grease interceptor is specifically designed for kitchen waste, not for the discharge from water treatment units. Discharging directly into the public sewage system might not provide adequate protection against contaminants entering the municipal water supply, particularly without a mechanism like an air gap that ensures safety and compliance with plumbing codes.