(a) A municipality shall impose and collect charges for services provided by a utility system in amounts at least sufficient to pay:
(1) all operating, maintenance, depreciation, replacement, improvement, and interest charges in connection with the utility system;
(2) for an interest and sinking fund sufficient to pay any public securities issued or obligations incurred for any purpose described by § 1502.002 relating to the utility system; and
(3) any outstanding debt against the system.
(b) The rates charged for services provided by a utility system must be equal and uniform. A municipality may not allow any free service except for:
(1) municipal public schools; or
(2) buildings and institutions operated by the municipality.

(c) The board of trustees having management and control of a utility system located in a county contiguous to the Gulf of Mexico and bordering the United Mexican States may impose and collect the charges authorized under this section for services provided by the utility system.