Where do lead and copper samples originate from?

Lead and copper samples specifically originate from customer plumbing fixtures directly because these metals are typically found in residential plumbing systems, particularly in older homes where lead pipes or lead solder may have been used. The sampling process is designed to assess the levels of both lead and copper that consumers might be exposed to through their drinking water.

When samples are taken from the plumbing fixtures, they reflect the potential contamination that could occur as water sits in the pipes for an extended period, allowing for any leaching of these metals into the water supply. This direct testing approach provides insight into the quality of drinking water that customers actually receive, which can differ significantly from the water quality at treatment facilities or within the distribution network.

The other choices involve points where lead and copper may not be present in significant amounts or may not give an accurate representation of the metals' levels actually experienced by consumers. Water that has been treated for safety may not reveal contamination that occurs later in the delivery process, which is why sampling directly from customer plumbing is essential for a precise assessment of lead and copper exposure risks.