A water-cooled distilling apparatus for purifying or distilling raw water. The apparatus includes a boiler, cooling tray assembly, and collection vessel. In use, raw water is initially poured into the boiler which has a self-regulating screen in it. As the water beings to boil, the screen rises to float above the raw water. The height of the screen above the water automatically adjusts proportionately to the rate of boil to proportionately expose more or less surface area of the screen. A water film forms on the exposed surface area of the screen and clean steam rises therefrom into the cooling tray assembly where it is deflected into a condensing area on each level of the assembly. In each condensing area, heat is transferred from the steam into coolant water in a reservoir, causing the coolant water to evaporate from the reservoir and the steam to condense on the bottom of the surface of the reservoir. Distillate formed by the condensing steam is then collected and transferred to a collection vessel.