D25/100
San Joaquin Tap Water Quality: Is It Safe to Drink? (2026 Report)
Serving 4,060 residents · California
What's In San Joaquin's Tap Water?
51
Contaminants Tested
0
Exceed EPA Limits
1
Above EPA Goals
1 contaminant above EPA health goals
| Contaminant | Detected | Limit (MCL) | Status |
|---|---|---|---|
manganese | 410.00 µg/L | — | Above Goal |
EPA Violation History
No violations in the past 5 years
Full EPA compliance since 2010.
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
SAN JOAQUIN, CITY OF
Population Served
4,060
Water Source
Groundwater
System ID
CA1010034
Frequently Asked Questions About San Joaquin Water
Is San Joaquin tap water safe to drink?
San Joaquin, California tap water receives a grade of D (25/100), which is considered poor. 0 contaminant(s) exceed EPA maximum contaminant levels and 20 violation(s) are on record. Residents should consider using an NSF-certified water filter to reduce contaminant exposure.
What contaminants are in San Joaquin's water?
Of the 51 contaminants tested in San Joaquin's water supply, the most notable include manganese. No contaminants exceed EPA legal limits. 1 contaminant(s) exceed EPA health goals (MCLGs), which are non-enforceable targets set at levels with no known health risk.
Does San Joaquin have any water quality violations?
Yes, San Joaquin has 20 EPA violation(s) on record, with the most recent in 2010. Violation types include MCL, MR, Other. 13 of these are health-based violations, which are the most serious category.
Do I need a water filter in San Joaquin?
San Joaquin 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. 1 contaminant(s) exceed these stricter goals.
Where does San Joaquin's tap water come from?
San Joaquin's drinking water is sourced from groundwater and supplied by SAN JOAQUIN, CITY OF. The system serves approximately 4,060 people. Groundwater is pumped from underground aquifers, which often provides natural filtration.
How often is San Joaquin'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. San Joaquin'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 San Joaquin's water compare to other cities in California?
San Joaquin's water quality score of 25/100 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 San Joaquin's water quality?
If you have concerns about San Joaquin'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 (SAN JOAQUIN, 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.