Is the Water Safe in Thornton, CO?
The 1 public water system serving Thornton, Colorado (population 226,465) average a Water Safety Score of 70/100, with a worst grade of C. These systems have no health-based violations on record.
Safety & Violations
| Metric | Value |
|---|---|
| Average Safety Score | 70/100 (C worst) |
| Public Water Systems | 1 |
| Population Served | 226,465 |
| Health Violations | 0 |
| Monitoring Violations | 13 |
| Contaminant Exceedances | 0 |
| Enforcement Actions | 22 |
Contaminants Detected in Thornton
| Contaminant | Detected | EPA Limit (MCL) | Status |
|---|---|---|---|
| Chlorine | 2 ppm | 4 ppm | Within limit |
| Gross Beta | 25 pCi/L | 50 pCi/L | Within limit |
| Uranium | 15 ppb | 30 ppb | Within limit |
| Gross Alpha | 7.5 pCi/L | 15 pCi/L | Within limit |
| Combined Filter Effluent | 0.5 NTU | 1 NTU | Within limit |
Detected levels are the highest reported across Thornton systems for each contaminant. MCL = EPA Maximum Contaminant Level, the legal safety ceiling. Source: EPA SDWIS monitoring data.
Frequently Asked Questions
The 1 public water system serving Thornton, Colorado (population 226,465) average a Water Safety Score of 70/100, with a worst grade of C. These systems have no health-based violations on record.
Monitoring data for Thornton, Colorado shows 5 distinct contaminants detected in the public water supply — Chlorine, Gross Beta, Uranium, Gross Alpha, Combined Filter Effluent. None exceeded the EPA Maximum Contaminant Level in the reported samples.
Thornton, Colorado is served by 1 public water system, together supplying water to roughly 226,465 people. The worst safety grade among them is C.
No. In the reported monitoring data for Thornton, no detected contaminant exceeded its EPA Maximum Contaminant Level (MCL).
The Water Safety Score (0-100, graded A-F) weighs health-based violations (40%), contaminant exceedances (30%), enforcement history (20%), and monitoring violations (10%), using EPA Safe Drinking Water Information System (SDWIS) data from the last 10 years.
Request your utility's annual Consumer Confidence Report (CCR), consider an independent test from a state-certified lab, and use an NSF-certified filter targeting any contaminant of concern. For lead specifically, run cold water 30 seconds before drinking.
More about Thornton
The 1 public water system serving Thornton, Colorado (population 226,465) average a Water Safety Score of 70/100, with a worst grade of C. These systems have no health-based violations on record.
The data source behind this answer is the EPA Safe Drinking Water Information System (SDWIS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
For readers turning this answer into action: cross-reference against the underlying the EPA Safe Drinking Water Information System (SDWIS) record before acting on time-sensitive decisions. The site renders the data as it was published; subsequent revisions can shift the picture, and the live federal data is always the authoritative current reference.
Source: EPA Ground Water and Drinking Water, 2026.