Collapsible reusable watertight carrying cases are provided in sizes varying from small containers to large sealable container bins on wheels, to provide large quantities of water to remote areas not served by public water supplies, or where water supplies are unavailable because of weather disasters. The cases are assembled or disassembled from a joined flat space-saving configuration to a functioning case and vice-versa. The sides of the cases are erected progressively by hand by interlocking elements at the corners. The panels also disassemble progressively by being manually pulled apart. When folded into a flat storage or shipping configuration, the panels stay together, resisting unfolding by virtue of snaps which are either molded into the panels or bonded to them. The carrying cases are resistant to water, dirt, bacteria, molds, allergens, and inclement weather.