Lost the third flow center (2013, 2017, 2021) on 5 ton Trane/WaterFurnace system due to erosion or corrosive conditions in closed loop system. Pumps developed leaks from pinholes. System was flushed the last two times with 1-micron filter sock in flush cart, water had red color and filter sock yielded what looked like rust particles. Had water analyzed this last time and the “standout” was a Langelier index (LSI) of minus 2.28 which we are told indicates very corrosive tendencies to cast iron (pump housing). Hard to understand as each time we flushed the system with potable water - no water treatment being used however. The ph was 6.68. Now the plan is to replace the water in the system with trucked in “pure water”, whatever that is. Anyone had similar experience? How would you go about removing the water in the system now? Thanks!