The board of commissioners of any district shall prescribe and collect reasonable rates, fees, tolls, or charges for the services, facilities and commodities of its system or systems, shall prescribe penalties for the nonpayment of the rates, fees, tolls, or charges, and shall revise such rates, fees, tolls or charges from time to time whenever necessary to ensure that such system or systems shall be and always remain self-supporting. The rates, fees, tolls or charges prescribed shall be such as will always produce revenue at least sufficient to: