California Code, Public Utilities Code - PUC § 774

No water corporation which has undertaken to provide fire protection service, nor any employee of such corporation acting in the course and scope of his employment, shall be liable for any death or injury to a person or damage to or loss of property resulting from a failure to provide or maintain an adequate water supply or pressure, or any equipment or other fire protection facility or service; provided, that such immunity from liability shall not exceed that of a public agency or any of its employees, as the case may be, under similar circumstances. Nothing in this section shall preclude the enforcement of any rule, regulation, or order of the commission.