... .Guarantee:15years 2.Certificate:SRCC,CE,Solar Keymark,ISO 3.Deliver time:Within 3days water heat pump DescriptionVacuum tube58-1800mm co-axial structure ... tank ,and the cold water sink to bottom,then heat by solar collector.so the whole system is always circulatingcontinuously.3,The ... the water is full,it will close the valve automatically solar water heat pump(CE,CCC,ISO)