Cal. Health & Safety Code § 111160

(a) Upon a determination by the department that a particular water source is subject to potential contamination, the department shall notify the bottler, distributor, or vendor of bottled water, the owner and operator of any water-vending machine, any water hauler, any retail water facility operator, or any private water source operator of the specific contaminants or class of contaminants that pose a potential health risk.
(b) Within 90 days after notification by the department, the bottler, distributor, vendor of bottled water, the owner and operator of any water-vending machine, any water hauler, any retail water facility operator, or any private water source operator shall conduct an analysis of the water source and submit the results of the analysis to the department.
(c) If evidence of contamination is found, the department may, by order, require the bottler, distributor, vendor of bottled water, or the owner and operator of any water-vending machine, any water hauler, any retail water facility operator, or any private water source operator to conduct a source and product water analysis for the contaminants of concern in accordance with conditions specified by the department. The water analysis shall be conducted and reported on an annual basis, unless the department finds that reasonable action requires either more frequent or less frequent analysis.
(d) The department may, by order, require the bottler, distributor, vendor of bottled water, the owner and operator of any water-vending machine, any water hauler, any retail water facility operator, or any private water source operator to reduce or eliminate the concentration of any chemical that the department determines may have an adverse effect on public health. Until an enforceable standard has been established for a chemical that may have an adverse effect on human health, the department may require treatment techniques to reduce the concentration of the contaminants that require treatment, in the department’s judgment, to prevent known or anticipated adverse effects on the health of persons. The treatment system shall be designed to meet criteria designated by the department or by an independent authority approved by the department.
(e) The department may grant variances from the requirements of subdivision (d), if the bottler, distributor, vendor of bottled water, the owner and operator of any water-vending machine, any water hauler, any retail water facility operator, or any private water source operator demonstrates either of the following:
1. (1) That the prescribed treatment technique is not necessary to protect the health of consumers because its water source is not subject to, nor is it likely to be subject to, significant chemical contamination.
2. (2) An alternative treatment technique is at least as efficient in lowering the level of contaminants to be controlled.