A portable water tank is a collapsible temporary tank designed for the reserve storage of water in firefighting, emergency relief, and military applications. These tanks can be either supported or unsupported. The supported tanks have a steel or aluminum frame and range in size from 600 to 5000 US gallons or larger by custom design. Portable water tanks are also unsupported such as self-supporting tanks (onion tanks), blivets and pillow or bladder tanks and are available in sizes ranging from 100 US gallons (380 L) up to 80,000 US gallons (300,000 L). The frame supported tank, for use in rural firefighting, is fully documented to have been invented in the early 1950s by Fol-Da-Tank Co. founder Giles Eldred, Rock Island,IL. Fol-Da-Tank Co. 's first patent for a spillway on the folding tank was applied for in 1954 and a patent for the "Float Dock" floating strainer for firefighting was applied for in 1955. Both patents were awarded in time. These products may be viewed athttp://www. fol-da-tank. com These products and many others have been supplied to the US Forest Service since the 1950s through distributors like Wajax, now known as Wildfire Equipment