The Heatsavr solter pool cover saves money by helping to prevent heat loss using a special liquid that sits on the surface of the pool virtually eliminating evaporation which is primary way pools lose their heat. This unique liquid is odorless, tasteless, non-toxic and 100% biodegradable so it’s safe for every pool and everyone. Just add a few ounces per week into the pool for best results. We recommend to use this product in the spring and fall or when the nighttime temperatures are cooler. That is when you pool loses the most heat!