C56/100
Half Moon Bay Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 18,940 residents · California
What's In Half Moon Bay's Tap Water?
69
Contaminants Tested
0
Exceed EPA Limits
2
Above EPA Goals
2 contaminants above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
chlorate | 380.00 µg/L | — | Above Goal |
Lead (90th percentile) | 0.002 mg/L | 0.015 mg/L | Above Goal |
EPA Violation History
No violations in the past 5 years
Full EPA compliance since 2008.
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
COASTSIDE COUNTY WATER DISTRICT
Population Served
18,940
Water Source
Surface Water
System ID
CA4110011
Frequently Asked Questions About Half Moon Bay Water
Is Half Moon Bay tap water safe to drink?
Half Moon Bay, California tap water receives a grade of C (56/100), which is considered fair. 0 contaminant(s) exceed EPA maximum contaminant levels and 14 violation(s) are on record. Residents should consider using an NSF-certified water filter to reduce contaminant exposure.
What contaminants are in Half Moon Bay's water?
Of the 69 contaminants tested in Half Moon Bay's water supply, the most notable include Lead (90th percentile), chlorate. No contaminants exceed EPA legal limits. 2 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.
Does Half Moon Bay have any water quality violations?
Yes, Half Moon Bay has 14 EPA violation(s) on record, with the most recent in 2008. Violation types include TT, MR, MCL. 6 of these are health-based violations, which are the most serious category.
Do I need a water filter in Half Moon Bay?
Half Moon Bay water meets EPA standards, so a filter is not strictly necessary. However, some residents prefer the added security of a water filter. EPA health goals (MCLGs) are stricter than legal limits and are set at levels with zero expected health risk. 2 contaminant(s) exceed these stricter goals.
Where does Half Moon Bay's tap water come from?
Half Moon Bay's drinking water is sourced from surface water and supplied by COASTSIDE COUNTY WATER DISTRICT. The system serves approximately 18,940 people. Surface water sources include rivers, lakes, and reservoirs.
How often is Half Moon Bay'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. Half Moon Bay'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 Half Moon Bay's water compare to other cities in California?
Half Moon Bay's water quality score of 56/100 earns a grade of C, which is considered fair. This is a below-average score that indicates room for improvement. Visit our California state page to see how all cities in the state compare.
What should I do if I'm concerned about Half Moon Bay's water quality?
If you have concerns about Half Moon Bay'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 (COASTSIDE COUNTY WATER DISTRICT) 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.