compact non pressure solar system 1.Certificates: CCC,ISO,CE,KEYMAEK 2.lifetime:15 years , ... .5mm5. insulation layer : polyurethane foam 55 mm 6. heat preservation: 72-80 hours 7. hail resistance: 25mm8. Optional: heat exchanger (red copper ... , and ensure the outlet water as stable temperature.3. Simple system, easy installation and low price. compact non pressure solar ...