D36/100
Castle Rock Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 4,367 residents · Washington
What's In Castle Rock's Tap Water?
52
Contaminants Tested
1
Exceed EPA Limits
1
Above EPA Goals
2 contaminants above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
Copper (90th percentile) | 1.40 mg/L | 1.30 mg/L | Over Limit |
Lead (90th percentile) | 0.005 mg/L | 0.015 mg/L | Above Goal |
EPA Violation History
2
Violations (last 5yr)
0
Unresolved
0
Health-Related
TIER 3Resolved
Failed Level 2 Assessment under Revised Total Coliform Rule
This is a paperwork/process violation — it does not mean a contaminant was detected at unsafe levels.
When: January 1, 2023 – December 31, 2023Rule: Stage 2 DBPREnforcement: Resolving — corrective action underway
TIER 3Resolved
Failed Level 2 Assessment under Revised Total Coliform Rule
This is a paperwork/process violation — it does not mean a contaminant was detected at unsafe levels.
When: January 1, 2023 – December 31, 2023Rule: Stage 2 DBPREnforcement: Resolving — corrective action underway
Understanding violation severity
Tier 1Urgent health risk. Utility must notify all customers within 24 hours.Tier 2Important health or treatment issue. Customers notified within 30 days.Tier 3Administrative or monitoring issue. Reported in the annual water quality report.
Source: EPA Safe Drinking Water Information System (SDWIS) · Updated quarterly
Water Utility Details
CASTLE ROCK MUNICIPAL WATER
Population Served
4,367
Water Source
Surface Water
System ID
WA5311800
Frequently Asked Questions About Castle Rock Water
Is Castle Rock tap water safe to drink?
Castle Rock, Washington tap water receives a grade of D (36/100), which is considered poor. 1 contaminant(s) exceed EPA maximum contaminant levels and 45 violation(s) are on record. Residents should consider using an NSF-certified water filter to reduce contaminant exposure.
What contaminants are in Castle Rock's water?
Of the 52 contaminants tested in Castle Rock's water supply, the most notable include Copper (90th percentile), Lead (90th percentile). 1 contaminant(s) exceed EPA legal limits (MCLs). 2 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.
Does Castle Rock have any water quality violations?
Yes, Castle Rock has 45 EPA violation(s) on record, with the most recent in 2023. Violation types include MR, TT. 2 of these are health-based violations, which are the most serious category.
Do I need a water filter in Castle Rock?
Based on EPA data, using a water filter in Castle Rock is recommended. 1 contaminant(s) exceed legal limits. An NSF-certified filter — such as a reverse osmosis or activated carbon system — can effectively reduce many common contaminants. Choose a filter certified to remove the specific contaminants found in your area.
Where does Castle Rock's tap water come from?
Castle Rock's drinking water is sourced from surface water and supplied by CASTLE ROCK MUNICIPAL WATER. The system serves approximately 4,367 people. Surface water sources include rivers, lakes, and reservoirs.
How often is Castle Rock's water tested?
Under the Safe Drinking Water Act (SDWA), water utilities are required to regularly test for over 90 contaminants. Testing frequency varies by contaminant — some are tested monthly, others quarterly or annually. Castle Rock's water systems must report results to the EPA and publish an annual Consumer Confidence Report (CCR). The data on this page reflects the latest available EPA testing data.
How does Castle Rock's water compare to other cities in Washington?
Castle Rock's water quality score of 36/100 earns a grade of D, which is considered poor. This is a concerning score that suggests significant water quality issues. Visit our Washington state page to see how all cities in the state compare.
What should I do if I'm concerned about Castle Rock's water quality?
If you have concerns about Castle Rock's tap water, consider these steps: (1) Request your utility's annual Consumer Confidence Report for detailed local data. (2) Get your water independently tested through a state-certified laboratory. (3) Consider an NSF-certified water filter rated for the contaminants found in your area. (4) Contact your water utility (CASTLE ROCK MUNICIPAL WATER) with specific questions. (5) Report water quality issues to your state drinking water program or the EPA Safe Drinking Water Hotline at 800-426-4791.