Dosing system for water treatment, wherein the dosing system comprises a filling device, a removal device and a holding device for a number of containers, characterized by - a number of containers, wherein each container is designed for storing a solution of a disinfectant or a solution of a pH correction agent or a solution of a flocculating agent, wherein the container comprises a flexible, foldable casing (1.1) and exactly one opening (1.2) for closing, filling and emptying, wherein the opening (1.2) is closable, wherein a non-flexible connection element (1.3) forming the opening (1.2) is provided with a thread (1.5) and a collar (1.6), wherein the thread (1.5) is an external thread, and wherein the casing (1.1) is in an at least partially folded delivery state in which it has been filled with disinfection granules or pH correction agent granules or flocculating agent granules and is fillable with the respective solution for a filled use state, wherein the solution is producible by adding water to the respective granules, - a fixing unit for fixing a connection element (1.3) arranged in the region of the opening (1.2) of the container, wherein the fixing unit is angular, wherein the connection element (1.3) is horizontally insertable into a slot of a horizontal leg fixing unit, wherein the slot of the horizontal leg of the fixing unit has a width which is less than the width of the collar (1.6) of the connection element (1.3), and - exactly one lance for filling and emptying a container, wherein the lance is fixable by means of the fixing unit, and wherein, in the lance, a first and a second line, which serve for filling or for emptying, are each led to the foot of the lance, and wherein the lance comprises a further line for degassing that terminates in an upper region of the lance. - a number of containers, wherein each container is designed for storing a solution of a disinfectant or a solution of a pH correction agent or a solution of a flocculating agent, wherein the container comprises a flexible, foldable casing (1.1) and exactly one opening (1.2) for closing, filling and emptying, wherein the opening (1.2) is closable, wherein a non-flexible connection element (1.3) forming the opening (1.2) is provided with a thread (1.5) and a collar (1.6), wherein the thread (1.5) is an external thread, and wherein the casing (1.1) is in an at least partially folded delivery state in which it has been filled with disinfection granules or pH correction agent granules or flocculating agent granules and is fillable with the respective solution for a filled use state, wherein the solution is producible by adding water to the respective granules, wherein the container comprises a flexible, foldable casing (1.1) and exactly one opening (1.2) for closing, filling and emptying, wherein the opening (1.2) is closable, wherein a non-flexible connection element (1.3) forming the opening (1.2) is provided with a thread (1.5) and a collar (1.6), wherein the thread (1.5) is an external thread, and wherein the casing (1.1) is in an at least partially folded delivery state in which it has been filled with disinfection granules or pH correction agent granules or flocculating agent granules and is fillable with the respective solution for a filled use state, wherein the solution is producible by adding water to the respective granules, - a fixing unit for fixing a connection element (1.3) arranged in the region of the opening (1.2) of the container, wherein the fixing unit is angular, wherein the connection element (1.3) is horizontally insertable into a slot of a horizontal leg fixing unit, wherein the slot of the horizontal leg of the fixing unit has a width which is less than the width of the collar (1.6) of the connection element (1.3), and - exactly one lance for filling and emptying a container, wherein the lance is fixable by means of the fixing unit, and wherein, in the lance, a first and a second line, which serve for filling or for emptying, are each led to the foot of the lance, and wherein the lance comprises a further line for degassing that terminates in an upper region of the lance.