Water is the major ingredient in a water soluble metalworking fluid mix. It may amount to as much as 90-99% of the mix as used. Therefore its importance in product performance can not be ignored. Corrosion residue scum rancidity foam excess concentrate usage or almost any metalworking fluid performance problem can be caused by the quality of the water used in making the mix. Untreated water always contains impurities. Some impurities affect drastically by reacting or combining with metalworking fluid ingredients. These impurities can change performance characteristics. Therefore water treatment is necessary to obtain the full benefits of water soluble metalworking fluids.