Total Dissolved Solids (TDS) is a measurement of everything in your water – good and bad. The amount of TDS in water affects its taste, too little TDS (soft water) , and water tastes flat and insipid. This is why many people find drinking pure water (such as distilled) to be unpleasant. Most water that has high levels of TDS will contain high amounts of calcium and magnesium. When those minerals are present, high levels of TDS in drinking water will cause an unpleasant aftertaste. When water has high levels of calcium and magnesium, it is called hard water; water with low levels of calcium and magnesium is called soft water. ... read more >>