Is Castle Rock, CO tap water safe?
Supplied by Town of Castle Rock · serves 110,298 people (27,865 connections) · Surface water · EPA ID CO0118010
Data: U.S. EPA · How we read the data · How we check it
Buys water from Parker Water & Sanitation District, Castle Pines Village Metropolitan District, Pinery Waterworks District. Treated water bought from another system can carry that system's contaminants.
Summary
No federal limits exceeded in EPA data.
- PFAS
- Detected, below limit2 of 29 PFAS found at least once. All averages below the federal limits.
- Lithium
- Above screening levelHighest result 25 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 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 Jun 2026. 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.
- Tested your own tap? Compare your result with these numbers. Moving? Compare this system with another.
- Read Town of Castle Rock's annual water quality report (Consumer Confidence Report). It lists every regulated contaminant tested and is usually on the utility's website or mailed with your bill, and you can also request it at (720) 733-6041. EPA: how to find it.
PFAS (“forever chemicals”)
EPA UCMR 5: 5 entry points tested May 2023 to Aug 2024. "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 Not detected Limit 4 ppt | – |
| PFOS Not detected Limit 4 ppt | – |
| PFHxS Not detected Limit 10 ppt | – |
| 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) Not detected Limit 1 | – |
| PFBS Not detected Guideline 2,000 ppt | – |
| PFBA Detected, below limit Guideline 6,000 ppt | 1.28 ppt |
| PFHxA Not detected Guideline 3,000 ppt | – |
| PFPeA Detected, no limit | 1.93 ppt |
29 PFAS tested, 2 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 11 of 12 samples. Highest result 25 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 ppb lead (Jan 2026 – Jun 2026). Below action level
Highest since 2016: 4 ppb (Jun 2020).
| Monitoring period | Lead (90th pct.) |
|---|---|
| Jan 2026 – Jun 2026 | 2 ppb |
| Jul 2025 – Dec 2025 | 2 ppb |
| Jan 2025 – Jun 2025 | 2 ppb |
Earlier results (9)
| Jul 2024 – Dec 2024 | 2 ppb |
| Jan 2024 – Jun 2024 | 2 ppb |
| Jul 2023 – Dec 2023 | 2 ppb |
| Jan 2023 – Jun 2023 | 2 ppb |
| Jul 2022 – Dec 2022 | 3 ppb |
| Jan 2022 – Jun 2022 | 2 ppb |
| Jul 2021 – Dec 2021 | 2.8 ppb |
| Jan 2021 – Jun 2021 | 2 ppb |
| Jul 2020 – Dec 2020 | 2 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 | 6.8 ppb | 300 ppb |
| Strontium | 0.5 ppm | 1.5 ppm |
| Molybdenum | 1.1 ppb | 40 ppb |
| Chlorate | 660 ppb | 210 ppb |
| Chromium-6 | 0.92 ppb | – |
Where it serves
Castle Rock
ZIP codes the system reported serving: 80104, 80108, 80109
Nearby utilities
- Parker Water & Sanitation District Parker · 8 mi
- Highlands Ranch Water & Sanitation District Highlands Ranch · 13 mi
- City of Englewood Englewood · 20 mi
- City of Aurora Aurora · 24 mi
- East Cherry Creek Valley Water & Sanitation District Aurora · 24 mi
- Consolidated Mutual Maple Grove Water System Lakewood · 26 mi
Questions
Is Castle Rock tap water safe to drink?
Most of Castle Rock gets its water from Town of Castle Rock. Town of Castle Rock 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 Castle Rock water have PFAS?
Yes. EPA's 2023–2025 testing of Town of Castle Rock found 2 PFAS at least once. None of the averages were above the federal limits.
What is the lead level in Castle Rock water?
The most recent 90th-percentile lead result for Town of Castle Rock is 2 ppb, for the period ending Jun 2026. 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 CO0118010: violations, enforcement and inspections, straight from EPA.
- EPA UCMR 5 data: the PFAS and lithium results (search the file for PWSID CO0118010).
- EPA SDWIS download: the lead results, population and violation records we use.
- The utility's annual water quality report (Consumer Confidence Report): ask Town of Castle Rock at (720) 733-6041, or see EPA's guide to finding it.
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.