... 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 tube, borosilicate glass 3.3.e, Water ... 364.6581800363502.90162 Vacuum tube stainless steel solar water heater