Tap Water Quality Report
Tap water quality in THORNTON, Colorado
Tap water in THORNTON, Colorado receives a grade of F (44/100) from TapWaterSafety.org. It's served by THORNTON CITY OF. The most significant water quality concerns are: PFAS contamination; Perfluorohexane sulfonate (PFHXS) significantly above health guideline; Haloacetic acids (HAA9) significantly above health guideline; Total trihalomethanes (TTHMs) significantly above health guideline. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.
What's in THORNTON's tap water
Top water quality concerns identified by the EPA and Environmental Working Group across the utility serving THORNTON.
PFAS contamination
Severe concernPerfluorononanoic acid (PFNA), Perfluorooctane sulfonate (PFOS) detected. PFAS are persistent chemicals linked to cancer and immune effects with no known safe exposure threshold.
Perfluorohexane sulfonate (PFHXS) significantly above health guideline
Moderate concernPerfluorohexane sulfonate (PFHXS) detected at 1.71 ppt, 1713x above the EWG health guideline of 0.001 ppt.
Haloacetic acids (HAA9) significantly above health guideline
Moderate concernHaloacetic acids (HAA9) detected at 31.3 ppb, 522x above the EWG health guideline of 0.06 ppb.
Total trihalomethanes (TTHMs) significantly above health guideline
Moderate concernTotal trihalomethanes (TTHMs) detected at 38.6 ppb, 257x above the EWG health guideline of 0.15 ppb.
EPA compliance record
Official U.S. EPA records for THORNTON CITY OF (system ID CO0101150) for the last 3 years. Checked 2026-10-07.
| Rule | Type | Since | Status |
|---|---|---|---|
| Interim and Long Term 1 Enhanced Surface Water Treatment Rule | Missed testing or reporting | 09/01/2023 | Resolved |
| Lead and Copper Rule | Missed testing or reporting | 07/01/2023 | Resolved |
Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.
Recommended filters for THORNTON
Filters matched to the specific contaminants in THORNTON's water supply.
Filter certified for PFOA/PFOS (NSF/ANSI 53 or 58)
$180-$750Reverse osmosis and some carbon block filters reduce PFAS. Look for certification to NSF/ANSI 53 or 58 for PFOA/PFOS.
Carbon filter certified for VOCs (NSF/ANSI 53)
$180-$599Activated carbon is effective for disinfection byproducts. Look for NSF/ANSI 53 VOC reduction.
Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.
All contaminants detected in THORNTON's tap water
Every contaminant identified, compared side-by-side against US EPA legal limits, the EU Drinking Water Directive (2020/2184), WHO Guidelines, and California's Public Health Goal. Why we show multiple standards →
| Contaminant | Detected | EWG US health-based |
EPA US legal |
EU DWD Europe |
WHO global |
CA PHG strictest US |
Tested sample year |
Status |
|---|---|---|---|---|---|---|---|---|
| Perfluorohexane sulfonate (PFHXS) PFAS |
1.71 ppt | 0.001 | 10.0 | — | — | — | — | 1713× over |
| Haloacetic acids (HAA9) Disinfection byproduct |
31.3 ppb | 0.06 | — | — | — | — | — | 522× over |
| Total trihalomethanes (TTHMs) Disinfection byproduct |
38.6 ppb | 0.15 | 80.0 | 100 | — | — | — | 257× over |
| Bromodichloromethane Disinfection byproduct |
11.8 ppb | 0.06 | — | — | — | — | — | 197× over |
| Dibromochloromethane Disinfection byproduct |
13.4 ppb | 0.1 | — | — | — | — | — | 134× over |
| Dibromoacetic acid Disinfection byproduct |
2.91 ppb | 0.03 | — | — | — | — | — | 97× over |
| Haloacetic acids (HAA5) Disinfection byproduct |
8.13 ppb | 0.1 | 60.0 | 60 | — | — | — | 81× over |
| Chromium (hexavalent) Heavy metal |
0.604 ppb | 0.02 | — | — | — | — | — | 30× over |
| Perfluorooctanoic acid (PFOA) PFAS |
2.55 ppt | 0.09 | 4.0 | 100 | 100 | 0.007 | — | 28× over |
| Dichloroacetic acid Disinfection byproduct |
4.02 ppb | 0.2 | — | — | — | — | — | 20× over |
| Perfluorononanoic acid (PFNA) PFAS |
0.114 ppt | 0.006 | 10.0 | — | — | — | — | 19× over |
| Chloroform Disinfection byproduct |
6.93 ppb | 0.4 | — | — | — | — | — | 17× over |
| Perfluorodecanoic acid (PFDA) PFAS |
0.089 ppt | 0.006 | — | — | — | — | — | 15× over |
| Bromoform Disinfection byproduct |
6.44 ppb | 0.5 | — | — | — | — | — | 13× over |
| Bromate Disinfection byproduct |
1.01 ppb | 0.1 | 10.0 | 10 | 10 | 0.1 | — | 10× over |
| Trichloroacetic acid Disinfection byproduct |
0.897 ppb | 0.1 | — | — | — | — | — | 9.0× over |
| Radium, combined (-226 and -228) Radiological |
0.31 pCi/L | 0.05 | 5.0 | — | — | — | — | 6.2× over |
| Perfluorooctane sulfonate (PFOS) PFAS |
1.46 ppt | 0.3 | 4.0 | 100 | 100 | 1 | — | 4.9× over |
| Uranium Radiological |
1.97 pCi/L | 0.43 | 20.0 | 30 | 30 | 0.43 | — | 4.6× over |
| Nitrate Inorganic |
0.355 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 2.5× over |
| Nitrate and nitrite Inorganic |
0.345 ppm | 0.14 | 10.0 | 11.3 | 11.3 | 10 | — | 2.5× over |
| Chlorate Disinfection byproduct |
438.0 ppb | 210.0 | — | — | — | — | — | 2.1× over |
| Molybdenum Other |
3.71 ppb | 40.0 | — | — | — | — | — | Below guideline |
| Barium Heavy metal |
44.2 ppb | 700.0 | 2000.0 | — | 1300 | 2000 | — | Below guideline |
| Selenium Heavy metal |
0.267 ppb | 30.0 | 50.0 | 20 | 40 | 30 | — | Below guideline |
| Monobromoacetic acid Disinfection byproduct |
0.204 ppb | 25.0 | — | — | — | — | — | Below guideline |
| Perfluoropentanoic Acid (PFPeA) PFAS |
8.07 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorohexanoic Acid (PFHxA) PFAS |
7.85 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Perfluorobutanoic Acid (PFBA) PFAS |
7.3 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| 2,4-D Pesticide/Herbicide |
0.0748 ppb | 20.0 | 70.0 | — | — | — | — | Below guideline |
| Monochloroacetic acid Disinfection byproduct |
0.194 ppb | 53.0 | — | — | — | — | — | Below guideline |
| Perfluorobutane sulfonate (PFBS) PFAS |
5.19 ppt | 2000.0 | — | — | — | — | — | Below guideline |
| Manganese Heavy metal |
0.246 ppb | 100.0 | — | 50 | 80 | — | — | Below guideline |
| Perfluoroheptanoic acid (PFHPA) PFAS |
1.3 ppt | 1000.0 | — | — | — | — | — | Below guideline |
| Strontium Radiological |
0.287 ppb | 1500.0 | — | — | — | — | — | Below guideline |
| Fluoride Inorganic |
0.651 ppm | — | 4.0 | 1.5 | 1.5 | — | — | Below guideline |
| Lithium Other |
27.0 ppb | — | — | — | — | — | — | Below guideline |
All values in the unit of the detected level. Red cells indicate the detected level exceeds that standard. Some contaminants have limits in some jurisdictions but not others (shown as —). The "Tested" column shows the year each contaminant sample was collected.
Sources: US EPA, EU Drinking Water Directive 2020/2184, WHO Guidelines, California OEHHA PHGs, EWG Tap Water Database.
Treatment plant contact info
For service issues, water quality concerns, or to request a Consumer Confidence Report from THORNTON CITY OF.