Specifying the water usage ratio for HVAC equipment is an increasing goal in high performance building designs. This session introduces the concept of saturation indices for heat transfer systems, and demonstrate the tools available for predicting water consumption, water treatment control limits and chemical treatment directives. Presenters explore how the indices can be utilized to develop a successful water treatment program which balance water consumption and equipment life. This seminar provides the engineer, owner and operator with the tools and understanding necessary, for an efficient HVAC system, regardless of local makeup water quality