Typically, lead gets into your water after the water leaves your local treatment plant or your well. That is, the source of lead in your home’s water is most likely pipe or solder in your home’s own plumbing. The drinking water entering our homes and business from public water systems in Connecticut is essentially lead-free. But, as water stands in your copper plumbing, lead from soldered joints can dissolve into the water. The longer water stands unused in these pipes, the more lead is dissolved in the water. See figure 1.
(figure available in print form)
[Source: EPA Environmental News, R-110, May, 1993.]
The most common cause is corrosion, a reaction between the water and the lead pipes or solder. Soft water, which lathers soap easily is a common cause of corrosion. All kinds of water may have high levels of lead.
One factor that increases corrosion is the practice of grounding electrical equipment, such as telephones to water pipes. Any electric current traveling through the ground wire will accelerate the corrosion of lead in pipes.
Lead contaminated drinking water is most often a problem in houses that are either very old or very new.
Up through the early 1900’s, it was common practice, in some areas of the country, to use lead pipes for interior plumbing. Lead piping was often used for the service connections that join residences to public water supplies. This practice ended only recently in some localities. Plumbing installed before 1930 is most likely to contain lead. Copper pipes have replaced lead pipes in most residential plumbing. However, the use of lead solder with copper pipes is widespread. Experts regard this lead solder as the major cause of lead contamination of household water in the U.S. homes today.
Scientific data indicate that the newer the home, the greater the risk of lad contamination. Lead levels decrease as a building ages. This is because, as time passes, mineral deposits form a coating on the inside of the pipes, if the water is not too corrosive. This coating insulates the water from the solder. But, during the first five years, before the coating forms, water is in direct contact with the lead. More likely than not, water in buildings less than five years old has high levels of lead contamination.