A.   All plumbing contractors, before doing work of any kind mentioned in this subchapter, except in cases of repairing leaks inside of property lines, shall file in the code enforcement office upon blanks for that purpose, an application for a permit and a plan or sketch of the work to be performed, and no work shall be done in any building without a written permit from the code enforcement office.
   B.   The number of the plumbing permit shall be posted conspicuously on the premises concerned so that it can easily be read. (2001 Code § 150.102)