A very low pressure and entirely mechanical sea water desalination device is described, which may be built and operated at a fraction of the current costs for the desalination of sea water. The desalination device is used to purify polluted or otherwise impure water and is a device is easily scaled and can be used in a very small facilities up to the largest facilities for desalinating or purifying water. The device operates with sunlight and ambient heat, and therefore will be very inexpensive to operate in desert and tropical regions; and slightly more expensive to operate in cooler regions, yet still substantially less expensive than the existing systems. The device reduces the cost of potable water made from sea water or other polluted sources to a level which is comparable to or less than the cost of such water received from traditional local fresh-water sources.