Section 27-931. Existing sprinklers

(a)  Required  sprinklers. Sprinkler
  systems  and  devices  existing  on  December  sixth,  nineteen  hundred
  sixty-eight  shall  not  be  required  to  be  altered to conform to the
  provisions of this subchapter, except that when additional protection is
  required for a change in occupancy or for a building addition,  the  new
  or  altered  part  of  the  system  shall  comply  with this subchapter.
  Sprinklers in any extension or alteration  shall  be  connected  to,  or
  extended  from,  the  existing  system  or  a  separate  water supply as
  provided  in  section  27-962  of  article  four  of  this   subchapter.
  Additional heads shall not be connected to existing undersized piping.
    (b)  Voluntary  sprinklers.  Sprinkler systems and devices existing on
  December sixth, nineteen hundred sixty-eight, but which are not required
  by this code, need not conform to the  provisions  of  this  subchapter,
  except  that  when a siamese hose connection is installed in the system,
  the siamese connection shall be installed and the entire system pressure
  tested as required by this subchapter.