Tex. Water Code § 54.2052

Notwithstanding any other law, a district is not required to adopt a plumbing code. A district may adopt and enforce one or more plumbing codes meeting the standards and requirements of the rules and laws of this state and may amend any code adopted to conform to local concerns if the amendment does not substantially vary from rules or laws of this state. If a municipal regulation conflicts with a district regulation, the municipal regulation prevails.