... efficiency 4.Unpressurized,more safe DEAKON unpressrized vacuum tube solar wate heaters Products features: 1, Modular design, ... effect.c, Water tank: inner tank is stainless steel(0.4 mm 304 food grade ),outer tank ... is stainless steel.d, Glass tube: new trivalent element heat ... .30142DK5818-364.6581800363502.90162 Vacuum tube stainless steel solar water heater