More than halfway through the second swim season I have officially certified them as legit! Pool water has not risen 1 degree over 85* in the last month even with temps in the 100's temperature is steady! Running the filter at night for 9 hours keeps the temp at 85*! During the daytime temperature rises up into the low 90's. By morning were back down to the low 80's. I see no change in evaporation levels at all! I add about 3"s of water a month. With all the doubters out there (including my neighbors), next time you jump into your HOT pool, take a handful of teabags with you!