311.1 General — 2025 California Plumbing Code

The drainage system of each new building and new work installed in an existing building shall be separate and independent from that of any other building, and, where available, every building shall have an independent connection with a public or private sewer.

Exception: Where one building stands in the rear of another building on an interior lot, and no public or private sewer is available or can be constructed to the rear building through an adjoining court, yard, or driveway, the building drain from the front building shall be permitted to be extended to the rear building.

Note: Accessory dwelling units are not required to have inde- pendent service utility (drainage) connections provided they meet the specific requirements in Government Code Section 65852.2.