Where does lead come from?

Category: Water Service Information

Finished water leaving the Wilmette water treatment plant historically has had no detectable lead. Lead in the water supply does not come from the treatment plant and water mains but rather from the plumbing that is located between the water main in the street and the inside of a house (typically referred to as the service line). Generally, there are three sources that could leach lead into the drinking water:

  • Lead Service Lines – A service line is the pipe that connects your house to the water main in the street. Some service lines that run from older homes (usually those built before 1940) to the utility water main are made from lead. Over time, some of these older service lines have been replaced, but many homes could still have one.
  • Lead-tin solder joined copper pipes – Copper piping has often been used since the 1930’s for home plumbing, but the solder (an alloy of tin with lead and antimony) used to fuse the pipes together typically contained elevated levels of lead prior to 1986, the year it was banned.
  • Household faucets and fixtures – Lead can also corrode from metal faucets and fixtures made from brass, an alloy of copper and zinc that often contains lead impurities, including chrome-plated brass fixtures. Therefore, a home with no copper or lead pipe could have elevated lead levels due to brass fixtures. Plumbing fixtures with a lead content of less than 8% used to be legally defined as “lead free” but since 2014, “lead free” refers to fixtures with a lead content of 0.25% or less.
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