D39/100
Patterson Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 25,304 residents · California
What's In Patterson's Tap Water?
66
Contaminants Tested
0
Exceed EPA Limits
2
Above EPA Goals
2 contaminants above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
strontium | 3200.00 µg/L | — | Above Goal |
chlorate | 400.00 µg/L | — | Above Goal |
EPA Violation History
No violations in the past 5 years
Full EPA compliance since 2007.
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
PATTERSON, CITY OF
Population Served
23,304
Water Source
Groundwater
System ID
CA5010017
WESTERN HILLS WATER DISTRICT/DIABLO GRAN
Population Served
2,000
Water Source
Surface Water
System ID
CA5010039
Frequently Asked Questions About Patterson Water
Is Patterson tap water safe to drink?
Patterson, California tap water receives a grade of D (39/100), which is considered poor. 0 contaminant(s) exceed EPA maximum contaminant levels and 48 violation(s) are on record. Residents should consider using an NSF-certified water filter to reduce contaminant exposure.
What contaminants are in Patterson's water?
Of the 69 contaminants tested in Patterson's water supply, the most notable include strontium, 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 Patterson have any water quality violations?
Yes, Patterson has 48 EPA violation(s) on record, with the most recent in 2018. Violation types include MR, MCL, Other. 35 of these are health-based violations, which are the most serious category.
Do I need a water filter in Patterson?
Patterson 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 Patterson's tap water come from?
Patterson's drinking water is sourced from groundwater and supplied by PATTERSON, CITY OF and 1 other water system(s). The system serves approximately 25,304 people. Groundwater is pumped from underground aquifers, which often provides natural filtration.
How often is Patterson'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. Patterson'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 Patterson's water compare to other cities in California?
Patterson's water quality score of 39/100 earns a grade of D, which is considered poor. This is a concerning score that suggests significant water quality issues. Visit our California state page to see how all cities in the state compare.
What should I do if I'm concerned about Patterson's water quality?
If you have concerns about Patterson'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 (PATTERSON, CITY OF) 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.