When a permit for a connection with a main for building purposes is issued, the service pipe must be carried to the outer edge of the sidewalk as in other cases, and when the building is completed, the pipe shall be taken up, the ferule drawn and the hole plugged, unless an extension is wanted to supply the building, in which case application must be made in the usual way. Rates for building purposes shall be payable on demand. (Ch. 79, 1-1-1922)