A method for producing a tank from thermoplastic material, comprising the following method steps: - extruding or providing a hose-like parison composed of plasticized thermoplastic material, and dividing and spreading the parison into two areal extrudate webs, or - extruding or providing two parisons in web form, - laying-in and molding the parisons in recesses of a multi-part blow-molding tool using differential pressure, wherein the recesses of the blow-molding tool delimit a mold cavity, - punching out, or cutting out in a circular shape, at least one opening in at least one shell-like intermediate product, wherein the opening is produced by way of a punching or cutting tool which penetrates through a wall of one of the shell-like intermediate products, wherein in a second method step, a first attachment element of a line connection or of a line arrangement is welded, at the mold cavity side to the wall of the shell-like intermediate product in such a way that an encircling weld collar of the first attachment element sealingly surrounds the opening, wherein the attachment element does not pierce or extend through the wall of the intermediate product and also does not protrude outward, - joining the shell-like intermediate products to form a tank, and removing the tank from the blow-molding tool, and - connecting a second attachment element, which is complementary to the first attachment element in the context of a plug-type connection, to the first attachment element, wherein the plug-type connection is produced within the contour of the tank as defined by the tank wall, characterized in that the punching out of the opening is carried out with a mold cavity side punching tool which is pushed through the wall of the shell-like intermediate product into a tool side die. - extruding or providing a hose-like parison composed of plasticized thermoplastic material, and dividing and spreading the parison into two areal extrudate webs, or - extruding or providing two parisons in web form, - laying-in and molding the parisons in recesses of a multi-part blow-molding tool using differential pressure, wherein the recesses of the blow-molding tool delimit a mold cavity, - punching out, or cutting out in a circular shape, at least one opening in at least one shell-like intermediate product, wherein the opening is produced by way of a punching or cutting tool which penetrates through a wall of one of the shell-like intermediate products, wherein in a second method step, a first attachment element of a line connection or of a line arrangement is welded, at the mold cavity side to the wall of the shell-like intermediate product in such a way that an encircling weld collar of the first attachment element sealingly surrounds the opening, wherein the attachment element does not pierce or extend through the wall of the intermediate product and also does not protrude outward, - joining the shell-like intermediate products to form a tank, and removing the tank from the blow-molding tool, and - connecting a second attachment element, which is complementary to the first attachment element in the context of a plug-type connection, to the first attachment element, wherein the plug-type connection is produced within the contour of the tank as defined by the tank wall,