Tex. Water Code § 49.234

(a) A district or water supply corporation that operates a wastewater collection system to serve land within its boundaries by rule may prohibit the installation of private on-site wastewater holding or treatment facilities on land within the district that is not served by the district's or corporation's wastewater collection system. A district or corporation that has not received funding under Subchapter K, Chapter 17, may not require a property owner who has installed an on-site wastewater holding or treatment facility before the adoption of the rule to connect to the district's or corporation's wastewater collection system.

(b) A district or water supply corporation that prohibits an installation described by Subsection (a) shall agree to pay the owner of a particular tract the costs of connecting the tract to the district's or corporation's wastewater collection system if the distance along a public right-of-way or utility easement from the nearest point of the district's or corporation's wastewater collection system to the boundary line of the tract requiring wastewater collection services is 300 feet or more, subject to commission rules regarding reimbursement of those costs.