A copper or bronze coupling must be used for all connections between iron and lead pipes. No iron pipe shall be used except by express permission of the utilities superintendent, and in that event the pipe must be heavily galvanized extra strong lap welded, and have the exposed threads thoroughly coated with coal-tar pitch applied hot. All pipe between the city water main and the property line shall be of ninety nine percent (99%) pure copper tubing tested at one thousand (1,000) pounds, internal hydraulic pressure, flanged at the ends and connected with suitable copper or bronze fittings; provided, that whenever conditions make such substitution advisable, the utilities superintendent may grant permission to use other material permitted under the current Minnesota plumbing code provided such approval is made in writing. (Ch. 79, 1-1-1922; amd. 1998 Code)