The EPA has been working to remove lead from drinking water for decades, yet it can still exist in trace amounts in municipal drinking water, or come from sources inside the home.
If your home was built prior to the 1980s, it's likely to have lead solder connecting the copper water pipes. Lead found in tap water often comes from corrosion of plumbing fixtures or the solder connecting the pipes. Today's plumbing fixtures must pass rigorous tests and be certified to contain levels of lead that are below safety thresholds.
Some major U.S. utilities use lead pipes to supply water from to homes and businesses. Because the pipes have been in use for a long time, they have formed a natural oxidation barrier that prevents lead from leeching into the water. Utilities will often add lime or orthophosphates as an additional barrier to prevent lead from getting into drinking water.
If you're concerned about lead in your home's drinking water, regular testing can help ensure that levels are safe to drink. In addition, EPA has an online guide called “How to Identify Lead Free Certification Marks for Drinking Water System & Plumbing Products” that can help you choose the right plumbing fixtures for your home.