... of the water, cold water down, hot water up, a cosmical physics, to circulat water through the collector and the tank. When water in the collectors ... and naturally rises into tank. Meanwhile, cooler water in the tank flows down to the collectors.Specifications:1. Material of inner water tank: 0 ... 5mm 304-2B(food-level stainless steel) 2. Material of outer water tank: 0.31mm, 0.4mm, 0.5mm stainless steel ...