Primary: each utility’s annual water quality report (Consumer Confidence Report, or CCR) and official utility pages; the U.S. EPA; the U.S. Census Bureau; USGS.
Certifications: NSF and EPA descriptions of the NSF/ANSI standards, and EPA’s WaterSense guide to water treatment systems.
Not used for facts: blogs, vendor sites, forums, third-party water databases, and AI summaries.
How we built the city guide
We ranked cities by the U.S. Census Bureau’s Vintage 2025 population estimates and picked each city’s main water utility.
From the latest annual report we could get, we recorded the disinfectant, hardness, and lead service line information, and we only state a fact if it appears in the cited document. A few reports don’t list hardness or name the disinfectant clearly. In those cases we used another official utility page, or we label the fact “Unverified” or “Not reported.”
PFAS results come from EPA’s final UCMR 5 dataset, filtered to the utility’s public water system ID. We count results at or above EPA’s minimum reporting level and show the highest. Results are reported in micrograms per liter, which we convert to parts per trillion (multiply by 1,000).
Hardness categories use the USGS scale. When a utility reports several plants or sources, we show the range.
An automated link check runs before every publish. Several utility and NSF sites block automated checkers, so we check those pages by hand and record the date.
Limits
Big cities can have more than one water provider, and water varies by neighborhood. Your own utility’s report is the authority for your address.
UCMR 5 is a snapshot from 2023 to 2025 sampling at treatment plants or entry points. Utilities may have changed treatment since.
Federal PFAS rules are changing. We note EPA’s May 2026 proposals and will update when they’re final.
Nothing here is medical, legal, or engineering advice.