Methodology
Data source
Every water system fact, violation and lead/copper result comes from the U.S. EPA Safe Drinking Water Information System (SDWIS/Fed), downloaded from the EPA Envirofacts API on October 30, 2026. New Hampshire DES reports this data to EPA each quarter, so recent events can take a quarter or more to appear.
Each system page shows the official system name and EPA ID (PWSID), the sampling and violation periods, when the data was imported, the units, and the legal limit where one applies.
Detection vs violation
- Detection: a lab found a substance. Many substances are detected at levels below the legal limit.
- MCL (legal limit): the highest level EPA allows. Going over it, usually as an average over time, is a violation.
- MCLG: a health goal with no enforcement. It can be zero (for lead it is zero).
- Action level (lead and copper): a trigger for extra steps such as corrosion control and public education. Exceeding it is not a violation by itself.
- Monitoring or reporting violation: a test or report was late or missing. It does not by itself mean a contaminant was too high.
No safety score
TapWaterPro does not label any water system safe or unsafe and does not compute a score. Records describe what was reported to EPA; they are not a test of your tap today.
Towns and ZIP codes
Towns are the primary city served listed by EPA. A town or ZIP code can be served by several systems, and we never guess which one serves an address. Check your water bill.
Which pages appear in search
A system page is offered to search engines only when its EPA record includes at least five dated lead/copper 90th-percentile results and a sampling period ending in 2023 or later. Town pages are offered only when they link to at least one such system page. Other pages stay available to visitors but are marked noindex until the data is complete.
Filters and links
We mention a filter only for a contaminant its NSF/ANSI certification covers. Any shopping link is an affiliate link and is labeled as one.