Water Quality in Castle Rock, CO: 12 Violations — Grade C
Grade C · Score 68/100 · 5 water systems · Updated 2026-05-03
Castle Rock's water has moderate compliance issues. Residents in affected areas should consider filtration.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
Tracked under the EPA Safe Drinking Water program, Castle Rock, CO shows 12 water violations on file — findings that span multiple violation categories and are detailed system by system in the data grid further down the page.
Water Quality by ZIP Code in Castle Rock
Water quality varies across Castle Rock's 3 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 80104 | C | 68 | 4 | 0 | View report → |
| 80108 | C | 68 | 4 | 0 | View report → |
| 80109 | C | 68 | 4 | 0 | View report → |
Water Quality Overview
Castle Rock, Colorado receives a water quality grade of C with an overall score of 68 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
The 5 water systems serving Castle Rock have accumulated 12 EPA violations (all monitoring/reporting type). These violations are tracked across 3 ZIP codes serving approximately 114,795 people.
What Grade C Means
A grade of C indicates moderate compliance issues. Castle Rock's water systems have some violations that warrant attention. While the water may still be safe for most people, residents in affected ZIP codes should consider additional testing or filtration.
Lead Levels
The average 90th percentile lead level across Castle Rock water systems is 0.0020 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
Radon Risk
Castle Rock is in EPA Radon Zone 1 (High risk). The EPA recommends all homes in Zone 1 areas be tested for radon. Radon is the second leading cause of lung cancer after smoking.
Water Systems Serving Castle Rock
Castle Rock is served by 5 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 114,795 people across 3 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
The EPA has taken 30 enforcement actions against water systems serving Castle Rock. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Castle Rock
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
Contaminants Detected in Castle Rock Water Systems
The following contaminants have been detected or caused violations across Castle Rock's water systems:
| Contaminant | Category | MCL | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|---|
| E. coli | Microbiological | N/A | 6 | 3 | No |
| Gross Beta | Radionuclides | 50 pCi/L | 3 | 3 | No |
| Lead and Copper Rule | Treatment Technique | N/A | 3 | 3 | No |
MCL = Maximum Contaminant Level (EPA enforceable standard). Health-based violations indicate levels that may pose direct health risks.
EPA Enforcement History
The EPA and state regulators have taken 10 enforcement actions against water systems serving Castle Rock. Recent actions:
| Date | Action Type |
|---|---|
| 2025-10-23 | State Informal Action |
| 2025-10-23 | State Informal Enforcement |
| 2025-08-07 | State Order Extension |
| 2025-07-18 | State Informal Action |
| 2025-07-18 | State Informal Enforcement |
| 2025-06-30 | State Informal Action |
| 2025-06-30 | State Informal Enforcement |
| 2025-04-23 | State Informal Action |
| 2025-04-23 | State Informal Enforcement |
| 2025-04-01 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2025-10-23.
Castle Rock vs. Nearby Colorado Cities
How Castle Rock's water quality compares to similar cities in Colorado:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Castle Rock | C | 12 | 5 | 114,795 |
| Avondale | D | 0 | 1 | 114,070 |
| Grand Junction | C | 14 | 5 | 117,739 |
| Broomfield | C | 8 | 4 | 109,723 |
Recommended Water Filters for Castle Rock
Based on contaminants detected in Castle Rock's water supply, these filter types are recommended:
Reverse Osmosis (under-sink)
- Removes: Arsenic, Barium, Nitrate
- Effectiveness: 90-99%
- Cost range: $150–$500
- Certification: NSF/ANSI 58
- Recommended products:
- Waterdrop G3P800
- iSpring RCC7AK
- Crystal Quest Arsenic Filter
Water Quality by ZIP Code in Castle Rock
Water quality varies across Castle Rock's ZIP codes. The table below shows the worst-scoring and best-scoring areas:
Common Questions About Castle Rock Water
These are the most common questions residents search for about water quality in Castle Rock, Colorado:
Is Castle Rock water hard or soft? Water hardness varies by source. Castle Rock's 5 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Castle Rock tap water? Castle Rock's water receives a grade of C (68/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Castle Rock? Based on detected contaminants, a reverse osmosis (under-sink) filter is most recommended. See our Water Filter Matcher for personalized recommendations.
Castle Rock vs. Colorado Average
Understanding how Castle Rock compares to the broader Colorado average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within Castle Rock.
ZIP Codes in Castle Rock
Castle Rock spans 3 ZIP codes. The ZIP with the lowest water quality score is 80104. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.