The size, slope, alignment, materials of construction
of a building sewer (gravity) and the methods to be used in excavating,
placing of the pipe, jointing, testing and backfilling the trench
shall all conform to the requirements of Part 1 or other rules and
regulations of the Town as applicable, but in no event shall the diameter
be less than four inches. The slope of such four-inch pipe shall be
not less than 1/8 inch per foot, unless otherwise permitted. In the
absence of code provisions or in amplification thereof, the materials
and procedures set forth in appropriate specifications of the ASTM
and Water Pollution Control Federation Manual of Practice No. 9 shall
apply.