Desalination of mild brackish water [800 ppm total dissolved solids (TDS)] has been demonstrated with a gain output ratio (GOR), also called the energy reuse factor, f, of I I using the dewvaporation technique. Dewvaporation process uses air as a carrier gas to evaporate water from saline feeds and to form pure condensate from dew at constant atmospheric pressure. The heat needed for evaporation is supplied by the heat released by dew fall condensation on opposite sides of a heat transfer wall. The external heat source can be from waste heat, solar collectors or fuel combustion. The unit is constructed out of thin water-wettable plastics and operated at pressure drops of less than 0.1'' of water. The product of the energy reuse factor, f, and the production density, P-f (mass rate of condensate production per area of heat transfer wall), is related to the maximum vapor content of the air. The value of the constant that relates the f*P-f to absolute humidity is composed of the properties of water vapor and the gas film heat transfer coefficient.