solar water heater : certification:ISO9001,ISO14001,CCC,CE,Solar Keymark solar water heater:heat pipe tube pressure:pressuriz solar water heater: material:1.volume of storage tank: ... ring gasket :EPDM4.evacuated tube:three-target tube,high boron and silicon,content 3.3,structure,gradual ... :1.can be operated completely automatic if connect with intelligent controller.2.Simple structure,easy plug-in ...