Is Thornton, CO tap water safe?
Supplied by City of Thornton · serves 226,465 people (42,530 connections) · Surface water · EPA ID CO0101150
Data: U.S. EPA · How we read the data · How we check it
Most of Thornton gets its water from City of Thornton. Parts of the city are served by 7 smaller systems: Todd Creek Village Metropolitan District (7,363 people), Woodland Hills Mhc Water System (1,740 people), Redwood Estates Water System (1,500 people), The Grove at Alta Ridge Water System (1,300 people) and 3 more. Your water bill names your system.
Summary
No federal limits exceeded in EPA data.
- PFAS
- Detected, below limit8 of 29 PFAS found at least once. All averages below the federal limits.
- Lithium
- Above screening levelHighest result 34 ppb. EPA uses 10 ppb to decide what to study further. It is not a health limit, and there is no federal limit for lithium. About 1 in 4 systems tested were above it.
- Lead
- Below action level2.3 ppb (parts per billion) at the 90th percentile: 9 in 10 homes sampled were at or below it. Action level 15 ppb, falling to 10 ppb in Nov 2027. Monitoring period ending Dec 2025. Your home's pipes can make yours higher.
- Violations
- None health-basedNo health-based violations since 2016.
- Built before 1986, or not sure what your service line is made of? Check your service line and test your tap. Utility data can't show your pipes.
- Want to reduce what was found? Filters for these results.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read City of Thornton's 2026 water quality report (Consumer Confidence Report, from the utility). It lists every regulated contaminant tested, including ones not on this page. Questions: (303) 255-7775.
PFAS (“forever chemicals”)
EPA UCMR 5: 2 entry points tested Feb 2023 to Nov 2023. "Average" is the highest entry-point average (non-detects counted as zero), the way EPA compares UCMR 5 results to the limits. ppt = parts per trillion. These results do not determine compliance.
| Contaminant | Highest average |
|---|---|
| PFOA One sample above limit Limit 4 ppt | 3.4 ppt 85% of the limit |
| PFOS One sample above limit Limit 4 ppt | 2.38 ppt 59% of the limit |
| PFHxS Detected, below limit Limit 10 ppt | 2.52 ppt 25% of the limit |
| PFNA Not detected Limit 10 ppt | – |
| HFPO-DA (GenX) Not detected Limit 10 ppt | – |
| Hazard Index (a combined score for PFHxS, PFNA, GenX and PFBS, where above 1 is over the limit) Detected, below limit Limit 1 | 0.26 |
| PFBS Detected, below limit Guideline 2,000 ppt | 5.63 ppt |
| PFBA Detected, below limit Guideline 6,000 ppt | 6.17 ppt |
| PFHxA Detected, below limit Guideline 3,000 ppt | 8.18 ppt |
| PFPeA Detected, no limit | 8 ppt |
| PFHpA Detected, no limit | 1.72 ppt |
29 PFAS tested, 8 detected at least once. "Not detected" means below EPA's reporting limit (about 2 to 20 ppt depending on the chemical), not proven zero. PFAS not listed were not detected. The limits for PFHxS, PFNA, GenX and the Hazard Index were proposed for rescission in May 2026. That proposal is not final. Systems have until 2029 to meet the limits.
Lithium
Detected in 7 of 7 samples. Highest result 34 ppb. EPA's non-enforceable screening level is 10 ppb. Above screening level The screening level is how EPA decides what to study further, not a health limit. There is no federal limit for lithium and no filter is certified to remove it. About lithium.
Lead and copper
Latest 90th percentile: 2.3 ppb lead (Jan 2025 – Dec 2025). Below action level
Highest since 2016: 2.5 ppb (Dec 2020).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2025 – Dec 2025 | 2.3 ppb |
| Jan 2024 – Dec 2024 | 1.4 ppb |
| Jul 2023 – Dec 2023 | 1.4 ppb |
Earlier results (9)
| Jan 2023 – Jun 2023 | 1.7 ppb |
| Jul 2022 – Dec 2022 | 1.6 ppb |
| Jan 2022 – Jun 2022 | 1.2 ppb |
| Jul 2021 – Dec 2021 | 2.2 ppb |
| Jan 2021 – Jun 2021 | 1.8 ppb |
| Jul 2020 – Dec 2020 | 2.5 ppb |
| Jan 2020 – Jun 2020 | 2.3 ppb |
| Jul 2019 – Dec 2019 | 1.4 ppb |
| Jan 2018 – Dec 2018 | 2.3 ppb |
Lead comes from pipes and fixtures, not the source water, so it varies home to home. The 90th percentile means 9 in 10 sampled homes were at or below it. More on lead.
Violations
Health-based violations mean a contaminant exceeded a limit or a required treatment step was missed. Monitoring and reporting violations mean required tests or reports were late or missing, so the water's quality during that time is unknown. The total includes every violation in EPA's records, most of them paperwork.
Earlier EPA testing (2013–2020)
| Contaminant | Highest | Guideline |
|---|---|---|
| Manganese | 0.83 ppb | 300 ppb |
| Chromium-6 | 1 ppb | – |
| Molybdenum | 4.8 ppb | 40 ppb |
| Chlorate | 1,100 ppb | 210 ppb |
| Strontium | 0.45 ppm | 1.5 ppm |
Where it serves
Thornton
ZIP codes the system reported serving: 80023, 80221, 80229, 80233, 80241, 80260, 80602
Nearby utilities
- Todd Creek Village Metropolitan District Thornton · same area · PFAS above limit
- County of Broomfield City and Broomfield · 6 mi
- City of Westminster Westminster · 7 mi
- South Adams County Water & Sanitation District Commerce City · 8 mi
- City of Brighton Brighton · 8 mi · PFAS above limit
- Denver Water Board Denver · 11 mi
Questions
Is Thornton tap water safe to drink?
Most of Thornton gets its water from City of Thornton. City of Thornton has no health-based violations since 2016. EPA testing found no PFAS above the federal limits. Federal data can't tell you about your own pipes: lead comes from service lines and plumbing, so test your tap if your home was built before 1986. For the official word, read the utility's annual Consumer Confidence Report.
Does Thornton water have PFAS?
Yes. EPA's 2023–2025 testing of City of Thornton found 8 PFAS at least once. None of the averages were above the federal limits.
What is the lead level in Thornton water?
The most recent 90th-percentile lead result for City of Thornton is 2.3 ppb, for the period ending Dec 2025. The federal action level is 15 ppb, falling to 10 ppb in November 2027. The 90th percentile means 9 in 10 homes sampled were at or below this number. Individual homes can be higher.
Check these numbers yourself
Every figure on this page comes from public EPA records. You don't have to take our word for it:
- EPA's own report for CO0101150: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID CO0101150).
- EPA SDWIS download: the lead results, population and violation records we use.
- City of Thornton's 2026 water quality report: the utility's own annual report, including contaminants EPA's national database doesn't carry (link checked Nov 14, 2026). Phone: (303) 255-7775.
- City of Thornton website
Found something that doesn't match? Tell us and we'll check it against EPA's records. How we check our data.
Source: U.S. EPA drinking water records and PFAS testing (UCMR 5). How we read the data.