... are conformed to prEN 13476-1(pipe & fittings), The ring stiffness rates are SN4 (ring stiffness over 4kN/m2 for sewerage), SN8 ... (ring stiffness over 8kN/m2 for sewerage) and ring stiffness over 6.3kN/m2 for communication ... service time, etc. The connection of piping system is O-ring gasket, ensuring no-leakage system.500mm-800mmdouble wall corrugated pipe,double ...