The local agency may enter into a written contract with a privately owned public utility rendering other than gas or electric service, that the charges for any sewer enterprise or service shall be collected together with and not separately from the charges of said privately owned public utility for any other utility service rendered by it, and that all charges shall be billed upon the same bill and collected as one item.
Source:
Section 54346.1, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV§ionNum=54346.1..