What is the second sample of water generally recommended to assess for lead contamination?

When assessing for lead contamination in water, the second sample typically recommended is a hot water sample. Hot water is often more effective in leaching lead from pipes and fixtures compared to cold water. This is because heat can enhance the solubility of lead and increase the interaction between the water and any lead that might be present in plumbing materials.

In many plumbing systems, lead can be found in solder, fixtures, and pipes, and hot water may flow through these materials more vigorously, allowing for a better assessment of potential lead levels. Collecting both cold and hot water samples can provide a more comprehensive view of lead exposure risks, but in practice, the hot water sample is often prioritized for analysis due to its capacity for revealing higher lead concentrations.

The cold water sample might not capture the same levels of lead, as it usually has less contact time with the plumbing materials. Piped water samples and filtered water samples have different purposes and don't specifically focus on assessing lead from plumbing exposure. Piped samples might not indicate the lead content at the tap level, and filtered samples can reduce or eliminate lead if a filter is working effectively, making it unsuitable for assessing lead presence.