Geothermal energy has been shown to be a cost-effective means of space-heating in adequately designed systems constructed of suitable materials. This paper deals with the interaction of conventional materials of construction for residential heating with geothermal fluid. Specific reference is made to the analysis of component failures from an apartment heating system. The mechanism of the corrosion induced failures is discussed. Recommendations for remedial action are presented, including the proper selection of materials for geothermal applications. Further study of the effect of specific geothermal fluids on system components and solders is indicated. The apartment heating system is compared to a larger system at an educational institution located in the same geothermal resource area.