Cal. Pub. Util. Code § 2701

Any person, firm, or corporation, their lessees, trustees, receivers or trustees appointed by any court whatsoever, owning, controlling, operating, or managing any water system within this State, who sells, leases, rents, or delivers water to any person, firm, corporation, municipality, or any other political subdivision of the State, whether under contract or otherwise, is a public utility, and is subject to the provisions of Part 1 of Division 1 and to the jurisdiction, control, and regulation of the commission, except as otherwise provided in this chapter.