S & T Mutual Water Company
EPA ID: CA4000523 · 591 people served · 1 ZIP code
ZipCheckup's reading of EPA records for S & T Mutual Water Company (CA4000523): no drinking-water violations recorded since 2021. EPA lists no violations for S & T Mutual Water Company, serving 591 people.
Data: EPA SDWIS
Service Area Map
Coverage area for S & T Mutual Water Company Source: EPA SDWIS service area boundaries.
Service area boundary
Demographics of ZIP Codes Served
The ZIP codes associated with S & T Mutual Water Company have a median household income of $103,839 and about 15,085 residents live in those ZIP codes (Census; not the number of people this system supplies). Approximately 80% of housing stock was built before 1986, which increases the likelihood of lead service lines and older plumbing.
💧 Where Does Your Water Come From?
S & T Mutual Water Company's water is classified in EPA records as a groundwater source. Groundwater is naturally filtered through rock and soil, but it can be vulnerable to PFAS contamination, nitrates from agriculture, and industrial chemicals that seep into the water table.
Infrastructure Risk
PFAS in ZIP Codes This System Serves
PFAS ("forever chemicals") have been reported in samples from water systems associated with the ZIP codes in this system's area. These results can come from other water systems serving the same ZIP codes; check the UCMR5 section for any results reported for this system. 8 detections recorded. 2 detections are above the level of a federal PFAS MCL (4 ppt for PFOA and PFOS), with compliance required from 2029.
Comparable Water Systems
Similar-sized systems in California
Estimated Remediation Costs
Average estimated costs across ZIP codes served by this system
Based on national averages for common remediation projects. Actual costs vary by property. Only issues flagged by EPA, FEMA, or state data for each ZIP code are included.
System Overview
S & T Mutual Water Company (EPA ID: CA4000523) is a community water system in California that serves approximately 591 people from groundwater sources.
This system serves ZIP code 93402 in Los Osos.
Violation History
Lead & Copper
EPA Lead and Copper Rule evidence attributed directly to this water system:
| Lead Level | Exceeds Action Level | Sample Date |
|---|---|---|
| 0.0011 mg/L | No | 2024-12-31 |
No copper action-level exceedance record appears for this PWSID in the accepted LCR snapshot. This does not establish a clean copper measurement.
Need help with your water quality?
Typical cost: Water test: typically $20–$50 (DIY kit) · Professional inspection: $150–$400
Find the Right Water FilterFree tip: Ask your water utility whether running cold water for 2 minutes is enough to flush your plumbing before drinking.
ZIP Codes Served
Coverage: Service area ZIP codes sourced from EPA Community Water System Service Area Boundaries v3 (March 2026 release). These ZIPs reflect the actual deployment footprint recorded by CA or modeled from parcel and building-footprint data.
- 93402 - Los Osos
Data Sources
This report uses public data from the EPA Safe Drinking Water Information System (SDWIS). View available EPA compliance records for S & T Mutual Water Company (CA4000523) on EPA.gov.
Frequently Asked Questions
Is S & T Mutual Water Company water safe to drink?
The accepted 2026Q2 ECHO snapshot contains zero violation records for S & T Mutual Water Company in the inclusive 2021-2026 record-year window. This is a compliance-record finding, not a guarantee about water at a specific tap.
How many people does S & T Mutual Water Company serve?
S & T Mutual Water Company serves approximately 591 people across 1 ZIP code in California.
Where does S & T Mutual Water Company get its water?
The primary water source is groundwater.
Frequently Asked Questions
How to cite this page
ZipCheckup. (n.d.). S and T Mutual Water Company Water Quality Report, CA. https://zipcheckup.com/water-system/ca4000523/
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