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, <EOS>