Cal. Health and Safety Code § 116735

(a) (1) In order to carry out the purposes of this chapter, a duly authorized representative of the state board may, at a reasonable hour of the day, do any of the following: (A) Enter and inspect a public water system or a place where the public water system records are stored, kept, or maintained. (B) Inspect and copy records, reports, test results, or other information required to carry out this chapter. (C) Set up and maintain monitoring equipment for purposes of assessing compliance with this chapter. (D) Obtain samples of the water supply. (E) Photograph a portion of the system, activity, or a sample taken. (2) An owner of a public water system shall provide to the state board reports, test results, and other information required to carry out this chapter within 15 business days of receiving a request for those records from a duly authorized representative of the state board. (b) The state board shall inspect each public water system as follows: (1) A system with any surface water source with treatment shall be inspected annually. (2) A system with any groundwater source subject to treatment with only groundwater sources shall be inspected biennially. (3) A system with only groundwater sources not subject to treatment shall be inspected every three years. (c) Nothing in this section shall prohibit the state board from inspecting public water systems on a more frequent basis. An opportunity shall be provided for a representative of the public water system to accompany the representative of the state board during the inspection of the water system. (d) It shall be a misdemeanor for a person to prevent, interfere with, or attempt to impede in any way a duly authorized representative of the state board from undertaking the activities authorized by paragraph (1) of subdivision (a). A person who violates paragraph (2) of subdivision (a) shall be subject to the provisions of Section 116730, as applicable.