Does “Soft” Water Assure a Spot-Free Car Wash?
“Hardness” in water refers to its calcium and magnesium content. “Softening” in the conventional sense means removing these minerals by exchanging sodium or potassium for them. When spotting occurs after a car is washed, “hardness” is usually blamed for the spots. This leads to the assumption that “softening” the water will produce a spot-free wash. Not necessarily so. Hardness represents only a part of the mineral content of water — the calcium and magnesium ions. Total mineral content, referred to in water treatment as TDS, or “Total Dissolved Solids,” is the real predictor of water’s spotting potential. The higher the TDS, the more spotting you’ll experience. Softening, contrary to popular belief, doesn’t take minerals out of the water. Rather, it exchanges sodium for the hardness minerals, calcium and magnesium, in more or less equal proportions. The TDS of softened water is essentially the same as that of hard water. Softened water has less calcium but more sodium. Softening is an
