Abstract: A low pressure, low temperature, solar powered evaporating-condensation system to provide relatively large scale conversion of brackish and seawater to fresh water, utilizes a solar radiation frequency selective material covered evaporation chamber, a throat connected elevated condenser containing energy transferring devices for vapor volume reduction to form a condensate which flows through a water-locked barometric leg to maintain the system at the sub-atmospheric pressure. The system is regenerative and includes means whereby the energy removed from the vapor during condensation is returned to the evaporating chamber and is again utilized in the cycle. Egress valves and locks are provided to maintain balanced flower of raw water, condensate and ejection of residuals. Suitable elevation of the condenser above the evaporator would provide for power generation.