Castle Rock, WA Tap Water Quality 2026

Water quality report for Castle Rock, WA — PFAS, lead and copper results, violation history and state inspection findings from EPA SDWIS.

A look at Castle Rock's drinking water using EPA enforcement records: violations, lead and copper results, PFAS sampling and state inspection findings.

Main Utility: Castle Rock Municipal Water PWSID: WA5311800 Updated: 2026 Q2

✅

No federal limits exceeded on record

Lead is 5.00 ppb, 33% of the action level and no violations are open. No PFAS was detected.

Castle Rock earns a B for water quality

Graded on violations, lead, and PFAS, with state inspection findings.

Lead: 5.00 ppb — 33% of the federal action level

PFAS tested, none detected

3 violations since 2015, 0 health-based

No violations currently open

Castle Rock's lead level vs. all Washington community water systems

0 ppb5 ppb10 ppb15 ppb

Lead level: 5.00 ppb — 33% of the federal action level

✓ Lower lead than 14% of Washington utilities

Population Served

2419

~1202 connections

Water Source

Surface water

Drawn from surface water — SDWIS source code SW

Active Violations

3 since 2015, all resolved

Lead & Copper Testing

Lead (Pb)

90th percentile of tap samples collected across the distribution system

33% of EPA action level

5.00 ppb

Action level: 15 ppb

Copper (Cu)

90th percentile of tap samples. SDWIS reports a copper figure only when a system exceeds the action level, so any value here is an exceedance.

107.7% of EPA action level

1,400 ppb

Action level: 1,300 ppb

The 90th-percentile lead result is 5.00 ppb, 33% of the 15 ppb federal action level. The action level is a treatment trigger, not a legal maximum, and it is measured across sampled taps rather than at any single home. Copper reached the action level here; a copper figure appears in SDWIS only when a system triggers it.

Contaminant Violations (2015–Present)

Contaminant	Type	Measured	Limit	Period	Status
Surface Water Treatment Rule	MONITORING AND REPORTING	—	—	2026	Resolved
TTHM	MONITORING AND REPORTING	—	0.080 mg/L	2023	Resolved
Total Haloacetic Acids (HAA5)	MONITORING AND REPORTING	—	0.060 mg/L	2023	Resolved

Understanding violation types MCL violations mean a contaminant exceeded the federal maximum limit — the most serious type.
TT (Treatment Technique) violations mean required treatment procedures weren't followed, but don't necessarily mean contamination occurred.

Violation History

3 violations are on record since 2015, of which 0 were health-based. All have been resolved and none remain open.

About the Main Water System

Utility Castle Rock Municipal Water

PWSID WA5311800

Water source Surface water — Drawn from surface water — SDWIS source code SW

Population served 2,419

Service connections 1,202

Systems serving this area 2

Regulator State primacy agency

Data through 2026 Q2 — EPA SDWIS

Frequently Asked Questions

Is Castle Rock tap water safe to drink? ▼

No federal limit is exceeded on record. No violations are currently open. Lead is 5.00 ppb, 33% of the action level.

Does Castle Rock water have PFAS? ▼

It was tested for the six regulated PFAS compounds and none were detected.

Who supplies water to Castle Rock? ▼

Castle Rock Municipal Water (PWSID WA5311800), one of 2 systems serving this area. Surface water. Drawn from surface water — SDWIS source code SW

When was this system last inspected? ▼

It was last inspected on 2024-10-16. No significant deficiencies were recorded.

What Should Castle Rock Residents Do?

Consider a filter certified for lead

Look for NSF/ANSI 53 certification for lead reduction.

Check for a lead service line

Lead reaches tap water mainly through service lines and household plumbing. Suppliers now publish an inventory identifying lead lines.

Flush before drinking

If water has sat in pipes more than six hours, run the cold tap for two minutes before drinking or cooking.

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