(a) If bonds issued under this subchapter are secured solely by a pledge of net revenue of the project, the commissioners court shall contract for and impose rates and charges for water supplied by the project that will be sufficient to:
(1) operate and maintain the project;
(2) pay when due the principal of and interest on the bonds; and
(3) establish any reserves provided in the order authorizing the issuance of the bonds.
(b) A bond secured solely by a pledge of net revenue:
(1) is not a debt of the county issuing the bond;
(2) may be a charge only on pledged revenue of a project;
(3) may not be included in determining the power of the county to issue bonds or incur other debt for any purpose authorized by law; and
(4) must contain the following provision: "The holder of this bond is not entitled to demand payment of this obligation out of any money raised by taxation."