... warranty for heat pipe solar water heater 3,Simple installation 4,Anti-freezing -40 degree Newest heat pipe split pressurized solar water heater(CE,SABS,Keymark, ... tube 2) The flow passage is inner closed and pressurized, no water or medium goes through glass vacuum tubes, no freeze ... original quality problems 2012 top sale heat pipe split pressurized solar water heater(CE,SABS,Keymark,EN12976)