I got this query recently from a climate-conscious friend of mine, contemplating the purchase of a solar heater: You end up losing 500 liters of water in 2-3 days due to evaporation.
He is not sure of the authenticity of this stat he stumbled upon on the web (http://www.mouthshut.com/review/V-Guard_Solar_Water_Heaters-177278-1.html). Clearly, clean potable water getting vaporized can't be good, but we need reliable and precise details before deducing anything. Your inputs would be greatly appreciated.