In the State of California and much of the west, Greywater Ready Construction regulations are now being adopted for residential and non-residential construction.
Graywater Ready, simply means that all new construction must have alternate piping installed at the time of construction to permit the discharge from clothes washers, showers, bathtubs, and bathroom/restroom wash basins to be used for a future graywater recycle or irrigation system. All graywater systems shall be designed with an approved diverter valve to allow the user to direct the flow to the building sewer or the irrigation field. (California Plumbing Code 1502.1)
The point of diversion/Stub-out of graywater to the sanitary drainage system shall occur downstream of fixtures and traps and vent connections through an Approved diverter valve, (CPC 1502.2.3) and shall be accessible (as defined in Section 99.02.202) and provided with signage that is satisfactory to the Department.
The Diverter/Stub-out is installed in the open position to the sanitary sewer until the future irrigation/recycling system is installed.