Every service pipe shall be laid so as to allow at least one foot of extra length in order to prevent rupture by settlement. The service pipe must be placed no less than eight feet below the ground and in a manner as to prevent rupture by freezing. Service pipes must extend from the curb stop box to the inside of the building, or if not taken into the building, then to the hydrant to fixtures which it is intended to supply. Type K copper tubing shall be used up to and including two-inch services. All underground joints are to be mechanical, except joints under floors shall be silver soldered, unless otherwise approved by the Public Works Supervisor. Joints of copper tubing shall be kept, to a minimum, with not more than one joint used for service for each 70 feet in length. Splicing may be approved with three-piece unions only. All joints and connections shall be left uncovered until inspected by the Public Works Supervisor and tested at normal water line pressure. Unions must be three-part type. All services over two inches shall be cast iron. Connections with the mains for domestic supply shall be at least one inch up to the curb stop box.