The rates to be charged for the service from such utility shall be sufficient to provide for the payment of interest upon all bonds and to create a debt service fund to pay the principal thereof as and when the same becomes due, and to provide for the operation and maintenance and repairs thereof and depreciation, and shall be revised from time to time so as to produce these amounts.

Source: SL 1931, ch 194, § 9; SDC 1939, § 45.2409; SL 1949, ch 191, § 4.