Cal. Welf. & Inst. Code § 6002

The person in charge of any private institution, hospital, clinic, or sanitarium which is conducted for, or includes a department or ward conducted for, the care and treatment of persons who are mentally disordered may receive therein as a voluntary patient any person suffering from a mental disorder who is a suitable person for care and treatment in the institution, hospital, clinic, or sanitarium who voluntarily makes a written application to the person in charge for admission into the institution, hospital, clinic, or sanitarium, and who is at the time of making the application mentally competent to make the application. A conservatee, with a conservator of the person, or person and estate, appointed under Chapter 3 (commencing with Section 5350) of Part 1 of Division 5, with the right as specified by court order under Section 5358 to place his conservatee, may be admitted upon written application by his conservator.

After the admission of a voluntary patient to a private institution, hospital, clinic, or sanitarium the person in charge shall forward to the office of the State Department of Mental Health a record of the voluntary patient showing such information as may be required by rule by the department.

A voluntary adult patient may leave the hospital, clinic, or institution at any time by giving notice of his desire to leave to any member of the hospital staff and completing normal hospitalization departure procedures. A conservatee may leave in a like manner if notice is given by his conservator.