99600c1d_Collector___Solar_Water_Heater__Evacuated_Tube_Collector
[S.No] 17 [Flat Plate Collector] Water quality effect the heating system forming scale over metal tube. [Evacuated Tube Collector] 
Water quality is not effect the system.
Comparison between Evacuated Tube Collector & Flat Plate Collector - Solar Water Heater
Evacuated Tube Collector