Abstract: A portable, collapsible tank for storing liquids which may be assembled in op, bottom, and side wall subassembly sections. The sections may be transported in compact substantially flat sections and easily assembled and disassembled in the field to provide greatly differing fluid capacities as desired. Arcuately segmented, interconnectable combination joining and supporting rings including sealing gaskets are provided for assembly and support of the multi-segmented relatively light weight top, bottom, and side wall subassembly sections fabricated of fiberglass or Kevlar type reinforced plastic materials. Segmented top and bottom walls are also formed of light weight, compact plastic material plate sections and are disposed atop and beneath the interposed wall sections. The tank assembly is further supported and stabilized by a center support pole in combination with top and bottom flange assemblies respectively.