A dehumidifier/cooling apparatus for use in a room having an elevated temperature and/or humidity is provided which utilizes the natural coolness of tap water to condense water vapor from the air or merely cool the air. The tap water line is diverted into a heat exchanger upstream of a hot water heater to dehumidify and/or cool the air in the room the air and remove the latent heat given off during condensation to cool and/or dehumidify the room air and to pre-heat the water entering the hot water heater. An air moving device powered solely by water moving through the tap water line directs a flow of air through the heat exchanger.