... system and 15 years for vacuum tube.Non-pressurized solar energy1.solar water heater with CE,3C,ISO9001,CNAL certificate;2 ... equipment;7.long life span and no extra cost after installation.MaterialInner tank: stainless steel SUS304/2B, 0.41mmOuter tank: ... electrical heating, assistant tankLogo: OEM, co lour printing /stickerFeature: 1.Solar water heater with CE,CCC,ISO ,CNAL certificate2.Special high ...