... offered 3 years guarantee nonpressure glass tube water heater High efficiency & high quality Nonpressure glass tube solar water heater 1. Specification ... *Copper coil: diameter 12mm,thickness 1mm length 30-45m *Heat Preservation: Polyurethane 50-60mm *Capacity:150L,160L,200L,250L ... pre-heated solar water heaterUse the copper coil as the heat exchanger, according to international fashion trend, it is ...