Connections to the main sewers or laterals must be made into a “Y” branch. Where no branch is available within a reasonable distance, a “Y” branch shall be inserted in the sewer line. In no case shall connections to any sewer of twelve inches diameter or less be made except into a “Y” branch fitting. Where sewer is tapped, a hub shall be cemented into a hole cut in the pipe and shall not protrude past the inside wall of the sewer pipe. Sewers shall not be tapped below the centerline of the pipe, and all taps shall be inspected and meet with the approval of the city engineer.