VNX-CDIT modules are unlike any other within the VNX family. These modules can tolerate up to 4 ppm feedwater hardness as CaCO3, up to 2 ppm feedwater silica as SiO2, and up to 100 μS/cm feedwater conductivity equivalent (FCE). To put it simply, these modules are optimized to provide high-purity water typically from a single-pass reverse osmosis (RO) feedwater supply with up to 90% recovery. Other modules, like the VNX-55, are limited to 1 ppm feedwater hardness, 1 ppm feedwater silica, and 40 μS/cm FCE.