Abstract: A water purification and/or desalination plant for producing drinking water from a polluted water source or sea water with the aid of sunlight, which plant includes an evaporator (1) having a roof part (2) made of a light-penetrable material, and an underlying basin part (3) containing the water that is to be purified, which basin part (3) includes channels (17) for collecting water vapor that has been condensed on the inside of the roof part (2), and a reservoir (10) for purified water. The plant also includes a device for removing moist air or vapor from the evaporator and a device for condensation of the moist air or vapor outside the evaporator.