Tex. Water Code § 13.513

A service provider shall not constitute a "water and sewer utility," a "public utility," a "utility," or a "retail public utility" within the meaning of this chapter as a result of entering into or performing a privatization contract, if the governing body of the eligible city shall so elect by ordinance and provide notice thereof in writing to the utility commission; provided, however, this provision shall not affect the application of this chapter to an eligible city itself. Notwithstanding anything contained in this section, any service provider who seeks to extend or render sewer service to any person or municipality other than, or in addition to, an eligible city may be a "public utility" for the purposes of this chapter with respect to such other person or municipality.