These include wooden or metallic frames, plastic or metallic pipes, organic sealants, glazing materials and insulation materials. Incompatibility of these materials is further aggravated upon exposure of SWH to different degradative environments such as intense solar radiation, high diurnal temperature variations, corrosive atmosphere and corrosive water. Although it appears that selection of materials in solar heaters is not of over-riding importance because there are no movable parts in the system, the latter is not immune to environmental degradation that is accelerated by the fluid system in use. Variations in fluid quality and prevailing environments could lead to change-over of mechanism of corrosion and also influence erystailine habits of scales : A. Anani, F. Abu-Allan and S. Kiwan, A three pronged approach to the study of eflicieney of solar water collectors in Jordan. Sol. Wind Technol. 5, 379 (1988). Jordan has long experience in the use of solar water heaters (SWHs)---the first system was installed as early as 1973. At the moment, more than one hundred thousand units are installed. A field survey was conducted to inspect the performance of materials under different climatic conditions and water quality prevailing in Jordan, so we can learn from its experience in this field.