Section 410. Undertakings to be self-supporting

The governing body of a
  municipality issuing bonds to carry out any  of  the  purposes  of  this
  article  shall  prescribe  and  collect reasonable rates, fees, tolls or
  charges  for  the  services,  facilities   and   commodities   of   such
  undertaking,  and  shall  revise such rates, fees, tolls or charges from
  time to time whenever necessary so that such undertaking  shall  be  and
  always  remain  self-supporting.  The  rates,  fees,  tolls  or  charges
  prescribed shall be such as will produce revenue at least sufficient (a)
  to pay when due all bonds and interest thereon for the payment of  which
  such  revenue  is  or  shall  have  been  pledged,  charged or otherwise
  encumbered, including reserves therefor, and  (b)  to  provide  for  all
  expenses  of  operation  and  maintenance of such undertaking, including
  reserves therefor.