It was also banned in household plumbing and limited in brass fixtures. Although illegal use of solder does continue, the EPA is considering further restrictions on the sale or manufacture of lead solder and brass fixtures that contain lead. Lead levels may be increased in homes that have naturally soft water. It is important, however, to make the distinction between a naturally soft water and softened water from a water softening device. Lead in drinking water is most commonly caused by the corrosion of lead plumbing materials.
Several factors cause water to be more corrosive than others.
According to the U.S. Geological Survey, more than 85 percent of the United States has hard water. However, in sections of New England and the far Northwest where naturally soft water is found, water tends to be corrosive because of its acidity, low TDS content, and the presence of dissolved oxygen. Since this natually soft water is corrosive, it is more likely to cause the corrosion of lead plumbing materials. In contrast, the process of softening water does not affect the characteristics that lead to corrosion, and therefore should not contribute to corrosion or to lead exposure. Water softening does not cause corrosion.