Method for manufacturing a storage tank comprising an inner liner, an outer filament winding and a connecting part. The method comprises the steps of: blow molding the inner liner by extruding a parison, pinching the inner liner at least at one extremity to create a pinch and then blowing the parison; providing the connecting part with a slot of appropriate shape and size to receive a part of the pinch; inserting the part of the pinch in the slot so as to secure the inner liner and the connecting part; and applying the outer filament winding around the liner and the connecting part.