All 1-1/2 in diameter and larger cast iron soil pipe and fittings for above and below grade soil, waste, vent lines, rain water conductors and storm drainage lines shall bear the registered insignia NO HUB® indicating that these items used in the sanitary system comply with the Cast Iron Soil Pipe Institute Standards 301 or ASTM A888. Tyler Pipe Company strongly recommends that its hubless cast iron pipe and fittings be joined with shielded couplings manufactured in accordance with CISPI 310. The use of unshielded couplings or any coupling not meeting the above specifications will void the product warranty.