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