(1) Tapered pipes complying with the requirements of C.A.S. No A16 shall be used when directly increasing in size of an earthenware sewer.

(2) The diameter of the ends of such tapered pipes shall correspond to the diameter of the pipes to which they are connected, and the gradient of such larger pipe shall not be decreased unless the soffit of the taper pipe is in line with that of the smaller pipe and on the same gradient.