P-902.3.1 In separate trench

For house drains installed beyond the building wall in a trench separate from water service or water distribution pipe, the drain pipe shall be of cast iron hard temper copper tube of a weight not less than type "L", vitrified clay pipe, concrete, or plastic. If the drain consists of plastic materials, the underground water service or water distribution pipe and the house drain shall be not less than 10 feet apart horizontally and shall be separated by undisturbed or compacted earth, or shall be in accordance with Section P-805 when approved by the Department.