Abstract: A tank structure for the storage and distribution of a plurality of fluids from several storage chambers located in an enclosure, wherein said chambers are constituted by several bags placed inside one another and formed by at least one fluid-tight wall made of a flexible material which, when unfolded, substantially fills the whole internal volume of the enclosure without being subjected to excessive stresses, said bags being provided with inlet and outlet valves for fluids stored in said chambers, said bags being surrounded by a housing at least one chamber forming an auxiliary chamber fed with pressurized auxiliary fluid from a source outside said housing, said pressure being transmitted from said auxiliary fluid to said fluids stored through said walls of flexible material of said bags.