Cal. Pub. Util. Code § 2702

Any corporation or association which is organized for the purpose of delivering water solely to its stockholders or members at cost, and which delivers water to others than its stockholders or members, or to the state or any department or agency thereof or any school district, or to any other mutual water company, for compensation, is a public utility and is subject to Part 1 (commencing with Section 201) and to the jurisdiction, control, and regulation of the commission.