Poolife Thermal ShieldPoolife Thermal Shield is a product that provides an invisible barrier that will help your pool to retain heat and help keep your water from evaporating. Using this product weekly can help reduce water loss from evaporation by up to 40%. Thermal shield also has a neutral pH, so it will not affect your water chemistry, and it will even work while swimmers are in the pool. Invisible barrier that prevents heat loss and conserves water Extends swim season