What is the water flowing out of the demineralizer to the condensate system called?

The term used to describe the water flowing out of the demineralizer to the condensate system is "polished water." This is because the demineralization process is designed to remove impurities and minerals from water, thus producing high-quality, clean water suitable for use in steam systems and other applications requiring low conductivity and high purity.

In this context, while "makeup feedwater" refers to water added to a system to replace losses, it does not specifically indicate the processed state of being treated through a demineralizer. "Processed water" is a more general term that does not adequately explain the specific purification that occurs within the demineralizer. "Return feedwater" typically refers to water returning from the condensate system back to the boiler or steam generator and does not describe the output of a demineralizing unit.

Therefore, "polished water" is the most accurate term to describe the treated water that exits the demineralizer and enters the condensate system.