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Updated 2026-10-15
County water report

Adams County Water Quality: 4 Cities Ranked by the Records

Adams County, Colorado: 4 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.

Find my systemOpen on the mapPrivate wells in Adams County
Across the county's systems

Highest result for each contaminant

One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.

LithiumDetected in 4 systems10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest34 µg/L
Perfluorooctanesulfonic acid (PFOS)Detected in 2 systems of 4 tested4.0 ng/L federal MCL (2024) · US EPAHighest10.6 ng/L
Perfluorooctanoic acid (PFOA)Detected in 2 systems of 4 tested4.0 ng/L federal MCL (2024) · US EPAHighest7.1 ng/L
Water hardnessDetected in 2 systemsAesthetic, no federal health limit · USGSHighest13.5 gpg
Perfluorohexanesulfonic acid (PFHxS)Detected in 2 systems of 4 tested10 ng/L federal MCL (2024) · US EPAHighest7.1 ng/L
Lead (90th percentile)Detected in 3 systems of 4 tested15 µg/L federal action level · US EPAHighest2.3 µg/L
Perfluorobutanesulfonic acid (PFBS)Detected in 2 systems of 4 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest8.1 ng/L
Perfluorohexanoic acid (PFHxA)Detected in 3 systems of 4 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest12.6 ng/L
3 more contaminants detectedShow
Perfluorobutanoic acid (PFBA)Detected in 3 systems of 4 testedNo federal or state limit; shown for transparencyHighest10.6 ng/L
Perfluoroheptanoic acid (PFHpA)Detected in 1 system of 4 testedNo federal or state limit; shown for transparencyHighest3.7 ng/L
  • THORNTON CITY OF3.7 ng/LSample date: 2023-02-14 to 2023-11-27
  • BRIGHTON CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-01-17 to 2025-08-19
  • SOUTH ADAMS COUNTY WSDNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-03-06 to 2024-12-16
  • WESTMINSTER CITY OFNot detected · below 3.0 ng/L lab reporting limitSample date: 2024-03-12 to 2024-12-04
Perfluoropentanoic acid (PFPeA)Detected in 3 systems of 4 testedNo federal or state limit; shown for transparencyHighest19.3 ng/L
21 PFAS tested, none detected in any systemShow

Tested in these 4 systems: BRIGHTON CITY OF, SOUTH ADAMS COUNTY WSD, THORNTON CITY OF, WESTMINSTER CITY OF

  • 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
  • 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
  • 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
  • 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
  • Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
  • N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
  • N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
  • Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
  • Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
  • Perfluoro-3-methoxypropanoic acid (PFMPA)
  • Perfluoro-4-methoxybutanoic acid (PFMBA)
  • Perfluorodecanoic acid (PFDA)
  • Perfluorododecanoic acid (PFDoA)
  • Perfluoroheptanesulfonic acid (PFHpS)
  • Perfluorononanoic acid (PFNA)
  • Perfluoropentanesulfonic acid (PFPeS)
  • Perfluorotetradecanoic acid (PFTA)
  • Perfluorotridecanoic acid (PFTrDA)
  • Perfluoroundecanoic acid (PFUnA)
4 cities

Cities ranked by the records

Showing 4 of 4 cities · scores are system-level, not tap tests

Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.

PFAS in Adams County2 of 4 city reports had a PFAS sample above a 2024 EPA limit
  1. Brighton10.6 ng/L
  2. Thornton5 ng/L
4.0 ng/L federal MCL · PFOS, ng/LPFAS in Colorado
Lead

0of 4 cities above the 15 µg/L action level

Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.

Lead in Colorado
Hard water

2cities report hardness · hardest Thornton, 13.5 gpg

2 of 2 are hard on the USGS scale. An aesthetic measure with no federal health limit.

Hard water explained
Who supplies the county

Largest water systems

  1. ThorntonTHORNTON CITY OF · CO0101150
    226,465 served
  2. WestminsterWESTMINSTER CITY OF · CO0101170
    202,078 served
  3. Commerce CitySOUTH ADAMS COUNTY WSD · CO0101140
    75,559 served
  4. BrightonBRIGHTON CITY OF · CO0101025
    56,304 served
Questions

Frequently asked

How does Adams County tap water compare across cities?

PurityMap ranks 4 cities in Adams County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Commerce City's main water system: SOUTH ADAMS COUNTY WSD · PWSID CO0101140 · Purity Score 100 (Excellent) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.

How many Adams County cities had a PFAS sample above a 2024 EPA limit?

2 of 4 Adams County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Brighton (PFOS 10.6 ng/L), Thornton (PFOA 7.1 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 3.

Is there lead in Adams County tap water?

Utilities report lead as a 90th-percentile result from home taps. 3 of 4 Adams County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.

Does Adams County have hard water?

Hardness is published in utility water-quality reports for 2 Adams County cities on record; the hardest is Thornton at 13.5 grains per gallon. Hardness affects scale and appliances; it is not a health finding.

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