Which of the following is excluded from gray water subsurface reuse systems?

The correct answer highlights that any means of recirculating gray water indoors is excluded from gray water subsurface reuse systems. This is significant because gray water subsurface reuse systems are typically designed for outdoor applications, primarily for irrigation or landscape purposes.

When gray water is used for irrigation, it needs to be treated properly to ensure safety and to protect public health. However, when it comes to indoor recirculation, there are more stringent health and safety regulations involved because the potential for direct human contact is greater. Indoor systems face challenges regarding contamination and monitoring that are not present in outdoor subsurface irrigation systems.

Thus, the exclusion of indoor recirculation from gray water subsurface reuse systems emphasizes the need for distinct handling and management of gray water depending on its intended use and environment, ensuring compliance with regulations and safeguarding human health.