Draining chamber and method of producing the same

Drainpipe comprises a corrugated plastic down pipe (1) with a sealed base (6) and connecting branches (3, 5). The base and branches are made in one piece with the down pipe, without welds. The down pipe has longitudinal reinforcing ribs (8). An Independent claim is included for a method for making the drain pipe by extruding a pipe and then blow-molding to corrugate the tube and simultaneously form the base and two connecting branches diametrically opposite each other.