The invention relates to a tank of plastics material produced by blow-molding of a parison, incorporating a welding spout, of a shape projecting from its outer surface which has an edge configured to be welded to a corresponding edge of an attached part, the welding spout ending axially, on an inside of the tank, in a shape resulting from contact molding between the parison and a molding component, in which the welding spout ends axially on an outside of the tank in a shape resulting from contact molding between the parison and a molding component.