# How to look up your own water system's PFAS results in EPA's UCMR 5 dataset

> EPA's final UCMR 5 dataset, released August 2026, covers about 10,130 water systems. Find your PWSID, read the result, and know why a non-detect means below 4 ppt.

| | |
|---|---|
| Source | https://ownerspec.com/water/guides/pfas-lookup-your-water-system-ucmr5/ |
| Publisher | OwnerSpec (https://ownerspec.com/) |
| Published | 2026-09-21 |
| Updated | 2026-09-21 |
| Facts verified | 2026-09-21 |

---

## Short answer

EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR 5) made community and
non-transient non-community water systems serving 3,300 or more people, plus a random
sample of 800 smaller ones, test for 29 PFAS and lithium between January 2023 and
December 2025. EPA released the final dataset in August 2026: approximately 10,130 public
water systems and about 25,950 sampling locations. To find your own system, take its PWSID,
a two-character state abbreviation followed by seven numbers, and search it in EPA's UCMR 5
Data Finder. If you have only a ZIP code, download the occurrence-data text files and match
it in UCMR5_ZIPCodes.txt. Then read the Result field slowly. UCMR 5 reports only results at
or above the minimum reporting level, and that level for PFOA and PFOS is 0.004 µg/L, which
is 4 parts per trillion. An entry of "<MRL" means below 4 ppt, not zero.

## Fact sheet

- **Answer:** EPA's final UCMR 5 dataset, released in August 2026, holds results for 29 PFAS and lithium from approximately 10,130 public water systems sampled between January 2023 and December 2025. You find your own system by its PWSID in EPA's UCMR 5 Data Finder. A result shown as "<MRL" for PFOA or PFOS means below 0.004 µg/L, which is 4 parts per trillion, not zero.
- **Basis:** EPA's UCMR 5 minimum reporting level of 0.004 µg/L for PFOA and PFOS, published in EPA's July 2026 UCMR 5 Data Summary, EPA 815-S-26-007.
- **Assumptions:** Public water system: UCMR 5 covers community and non-transient non-community systems serving 3,300 or more people, plus a random sample of 800 smaller ones.; Private wells were never in scope and appear nowhere in the dataset.; A UCMR 5 average is two or four samples over 12 months and is not a compliance determination.
- **Method:** Dataset scope, reporting levels and exceedance percentages read from EPA's July 2026 UCMR 5 Data Summary and EPA's Data Finder instructions, both cited in this page's sources.
- **Primary source:** [EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary, July 2026, EPA 815-S-26-007 (PDF)](https://www.epa.gov/system/files/documents/2023-08/ucmr5-data-summary_0.pdf) (government or regulatory source)
- **Facts verified:** 2026-09-21
- **Last updated:** 2026-09-21
- **Canonical URL (cite this):** https://ownerspec.com/water/guides/pfas-lookup-your-water-system-ucmr5/

If you drink from a private well, stop here: UCMR 5 never covered wells, and no amount of searching will produce a row for yours.

## What do you need before you can look anything up?

One identifier. Everything else in the dataset hangs off it.

| What you have | Where it takes you | Watch for |
|---|---|---|
| The PWSID printed on your water bill or annual water quality report | Straight into the UCMR 5 Data Finder's PWS ID filter | Utah systems start with the letters UTAH plus five numbers, not a two-letter code |
| The water system's name only | EPA's [Find Your Local Consumer Confidence Report](https://ordspub.epa.gov/ords/safewater/f?p=136:102) search, by state and city | Two systems in one county can carry similar names |
| A ZIP code only | UCMR5_ZIPCodes.txt inside each occurrence-data zip, which lists the ZIP Codes for all areas served by a system | EPA notes ZIP Codes are entered by the system and may not be available for every one |

A PWSID is the code EPA uses to identify each public water system. EPA's data definitions
state it begins with the standard two-character postal state abbreviation, or a Region code
for Tribes, and the remaining seven numbers are unique to that system within the state.

## Where do the UCMR 5 results actually live?

Two places, and they answer different questions.

The [UCMR 5 Data Finder](https://www.epa.gov/dwucmr/fifth-unregulated-contaminant-monitoring-rule-data-finder)
is the browser route. It filters by PWS ID or name, system size, state, EPA Region,
contaminant, source water type, results at or above the MRLs, and results above health-based
reference concentrations. Its Regulated PFAS Average Results tab is the one that matters for
PFOA and PFOS. Results are given in micrograms per litre.

The occurrence-data zips are the bulk route, in three cuts: all results, by state, and by
method classification. Either way, EPA caps an Excel download at one million records, so
filter the table down before pressing the button.

## Why is a non-detect not a zero?

Because a minimum reporting level is a laboratory limit, not a health limit.

EPA defines the UCMR MRL as the quantitation limit considered achievable with 95% confidence
by at least 75% of laboratories nationwide using the specified method, and states plainly
that MRLs are not associated with health effects information. Only results at or above it
reach EPA at all.

| Contaminant | UCMR 5 MRL (µg/L) | Same number in ppt |
|---|---|---|
| PFOA | 0.004 | 4 |
| PFOS | 0.004 | 4 |
| PFHxS | 0.003 | 3 |
| PFNA | 0.004 | 4 |
| HFPO-DA (GenX chemicals) | 0.005 | 5 |
| PFBS | 0.003 | 3 |
| Lithium | 9 | 9,000 |

Read the PFOA row twice. The reporting level and the 4.0 ppt Maximum Contaminant Level are
the same number, so "<MRL" tells you the compound was not quantified at the limit, and
nothing about what sits underneath it. In the Data Finder that shows as "< MRL" in the
Result field; in the text files the AnalyticalResultValue is blank and AnalyticalResultSign
reads "<".

## What if your system has no row at all?

EPA's instructions list the reasons, and most of them are not about your water.

1. The system serves fewer than 3,300 people and was not drawn into the random sample of 800.
2. It is a transient non-community system, which UCMR never covered.
3. The PWSID or name changed between UCMR cycles.
4. Sampling failed quality control after repeated resampling attempts.
5. The system was out of compliance and did not collect all its samples.

## How often was a system above a PFAS limit?

Less often than the headlines, and more often in cities.

EPA's July 2026 summary compares each sampling location average against the April 2024
limits. Among systems with a full set of results, an average above the PFOS limit turned up
at 12.2% of large systems (serving more than 10,000 people), 6.0% of medium systems
(3,300 to 10,000) and 5.8% of small ones. For PFOA the figures are 11.0%, 5.4% and 4.4%.
Taking all six limits together, EPA's weighted national estimate is that 7.8% of systems
have one or more averages above a PFAS limit.

A secondary analysis by Pace Analytical, published 22 April 2026, put PFOA at around 8% of
participating systems and PFOS at 8.9%. Those figures come from EPA's January 2026 interim
summary, which the July 2026 final edition supersedes, so prefer EPA's numbers above.

One more thing the dataset shows: EPA reports that 66% of sampling locations with any PFAS
at or above an MRL had more than one, and 3,183 locations had three or more.

**Before you buy a filter**

Do not order anything until the lookup is finished. If the Result field reads "<MRL", you
have no number to size against, and a certified filter is a preference rather than a
response to a measurement. If it reads a figure, the decision is a certification question,
not a brand question: the [PFAS in tap water filter guide](/water/guides/pfas-in-tap-water-what-filter/)
sets out which NSF/ANSI listing actually names PFOA and PFOS.

## What should you do first?

1. Find the PWSID on your water bill or annual water quality report.
2. Open the UCMR 5 Data Finder and filter by that PWS ID.
3. Go to the Regulated PFAS Average Results tab and note the sampling location averages.
4. Check whether each result is a number or "<MRL", and remember the 0.004 µg/L floor.
5. For a tap-level figure rather than an entry-point one, order a laboratory panel and read it with the [water test report guide](/water/guides/how-to-read-a-water-test-report/).

<!-- FAQ and Sources render from front matter. Do not write them in the body. -->

## Frequently asked questions

### What is a PWSID and where do I find mine?

A PWSID is the identification code EPA uses for each public water system. EPA's data definitions state the code begins with the standard two-character postal state abbreviation, or a Region code for Tribes, followed by seven numbers unique to that system. Utah is the exception: its codes begin with the four letters UTAH followed by five numbers. Your water bill or annual water quality report usually prints it.

### Does "<MRL" in the UCMR 5 results mean there is no PFAS in my water?

No. EPA's instructions state that only analytical results at or above the UCMR minimum reporting level are reported to the agency. For PFOA and PFOS that level is 0.004 µg/L, which is 4 parts per trillion. A "<MRL" entry means the laboratory did not quantify the compound at or above 4 ppt. It is not a measurement of zero.

### My system is not in the UCMR 5 dataset at all. Why?

EPA lists several reasons. The system may never have been required to monitor: UCMR 5 covered systems serving 3,300 or more people, plus a nationally representative random sample of 800 smaller ones. Transient non-community systems were excluded entirely. Private wells were never in scope. System IDs and names also change between UCMR cycles.

### Do UCMR 5 results show whether my system is in violation?

No. EPA states that UCMR 5 results for the regulated PFAS do not indicate compliance or noncompliance with the MCLs. Compliance is determined from a running annual average of quarterly compliance-monitoring results reported to the state primacy agency. UCMR 5 collected two samples per location on ground water and four on surface water, over a single 12-month window.

### Where were the UCMR 5 samples actually taken?

At the entry point to the distribution system, not at a household tap. EPA's dataset records each result against a facility and sample point at the water system. Anything the distribution network or your own plumbing adds after that point is outside UCMR 5, which is one reason a tap test and a UCMR 5 figure can disagree.


## Sources

- [EPA, Occurrence Data from the Unregulated Contaminant Monitoring Rule](https://www.epa.gov/dwucmr/occurrence-data-unregulated-contaminant-monitoring-rule) (government or regulatory source)
- [EPA, The Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) Data Summary, July 2026, EPA 815-S-26-007 (PDF)](https://www.epa.gov/system/files/documents/2023-08/ucmr5-data-summary_0.pdf) (government or regulatory source)
- [EPA, Fifth Unregulated Contaminant Monitoring Rule Data Finder](https://www.epa.gov/dwucmr/fifth-unregulated-contaminant-monitoring-rule-data-finder) (government or regulatory source)
- [EPA, Instructions for Accessing Unregulated Contaminant Monitoring Rule (UCMR) Results, January 2025, EPA 815-B-25-002 (PDF)](https://www.epa.gov/system/files/documents/2024-04/instructions-for-accessing-ucmr-results.pdf) (government or regulatory source)
- [EPA, Find Your Local Consumer Confidence Report](https://ordspub.epa.gov/ords/safewater/f?p=136:102) (government or regulatory source)
- [Pace Analytical, Making Sense of UCMR 5 Results: Key PFAS Findings, Lithium Concerns, and UCMR 6 Signals (April 22, 2026)](https://www.pacelabs.com/analytical-environmental/making-sense-of-ucmr-5-results-key-pfas-findings-lithium-concerns-and-ucmr-6-signals/) (manufacturer or vendor document)

---

Citation: OwnerSpec, "How to look up your own water system's PFAS results in EPA's UCMR 5 dataset", https://ownerspec.com/water/guides/pfas-lookup-your-water-system-ucmr5/, facts verified 21 September 2026.
Canonical citation target: the URL above (the public HTML page), not this Markdown representation.
Reuse: quoting with attribution and a link is permitted. See https://ownerspec.com/legal/terms/.