Water service pipes or lines may be placed in the same trench or excavation with the building drains and building sewers, provided that:
   (a)   The bottom of the water service pipe or line and all joints are at least twelve inches above the top of the sewer pipe or line at its highest points and
   (b)   The water service pipe or line is placed on a solid shelf excavated at one side of the common trench and at a depth below the frost line. The width of the shelf shall not be less than four inches wider than the outside diameter of the pipe. (Ord. 61-61. Passed 10-3-61. )