Practical guide
How to read UCMR 5 results
UCMR 5 is a nationwide monitoring program for 29 PFAS and lithium. Its occurrence data can show what a utility measured, where and when—but a detection is not by itself a violation or a test of your household tap.
A clearer perspective.
Start with the sampling location
Results generally describe water entering a distribution system. Compare repeated results from the same entry point together. A system may have several entry points fed by different sources, so combining every sample into one system-wide mean can hide that structure.
Detection and minimum reporting level
A reported detection is at or above the program's minimum reporting level. “Not detected” means the laboratory did not report a value at or above that level; it does not prove the contaminant was entirely absent.
Use the right comparison basis
For PFOA and PFOS, this site compares EPA's limit with the average from a complete monitoring set at one sampling location. The highest single sample is still shown, but it is not substituted for the required average. Non-regulatory reference levels are labeled separately from enforceable limits.
Check units and dates
PFAS results are commonly shown in parts per trillion (ppt, equivalent to ng/L). Lithium is shown in µg/L. Always compare values only after confirming compatible units and read the sampling window beside the result.