Abstract: Disclosed are apparatus and method for heating water by reflux condensation wherein a solar vaporized heat transfer fluid passes through a condenser in heat exchange relationship with a volume of water. The collection of solar radiation is effected in a primary solar collection region elevated above the condenser. The invention disclosed provides for the recirculation of condensed heat transfer fluid from condenser to the primary collection region. Sequentially, this entails passing condensate by gravity from the condenser into a U-type trap for accumulation until excess condensate causes some spill-over and flow by gravity of condensate into a booster solar collection region, through a venturi. In the booster regin spill over condensate flash vaporizes and is channeled in reverse through the venturi. The velocity of the vapor in the venturi creates low pressure according to the venturi effect, thereby drawing condensate accumulated in the trap into the venturi.