waterbycounty
Federal water data

County water report

San Francisco County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for San Francisco County, California.

Water grade

A

Water score

86.0

State rank

#1

of 58

Health violations

0

EPA SDWIS, 5-year lookback

Watershed impaired

28.1%

32 water bodies assessed

Monitoring sites

31

18,429 recent measurements

Live streamflow

No gauge

Primary USGS station not mapped

Water at a glance

Key Water Indicators for San Francisco County

EPA SDWIS

Safety Grade

A

Score: 86.0 / 100

EPA SDWIS

Active Violations

0

5-year health-based lookback

EPA ATTAINS

Watershed Health

28% impaired

32 bodies assessed

USGS NWIS

Streamflow Snapshot

No gauge

Primary USGS gauge not mapped

EPA WQP

Monitoring Sites

31

18,429 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

A

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

86.0/100

Health violations

0

Health-based violations

Violations per 100K served

0.0

Population-normalized SDWIS rate

Data center water stress

San Francisco County has 9 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #9 nationally by combining its water score with mapped data center density.

DCWSIThe Data Center Water Stress Index: 60% the county's water-system stress plus 40% how concentrated data centers already are, scored 0-100. Higher means data-center density and water pressure overlap more here.

85.8

0-100 index

Facility count

9

85.4 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+36.0

Compared with US county median

Named operators

AWS

Mapped facilities

  • 360 Spear Street Data Center

    San Francisco · Digital Realty

    OSM

  • 365 Main Street Data Center

    San Francisco · Digital Realty

    OSM

  • AMAZON DATA SERVICES, INC - SFO8

    SAN FRANCISCO · Amazon Data Services

    EPA ECHO

  • AT&T

    SAN FRANCISCO

    EPA ECHO

  • Digital Realty San Francisco SFO10

    San Francisco · Digital Realty

    OSM

  • KAISER PERMANENTE

    SAN FRANCISCO

    EPA ECHO

3 more mapped facilities included in the county score.

See the San Francisco County data-center reportReview methodology

Data Center Water Budget Calculator

Estimate daily water use for a hypothetical facility in San Francisco County.

1 MW1,000 MW
40%100%
799K gallons/dayHigh Impact

Your facility would use 39.4% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

39.4% of county industrial baseline1.23 Mgal/day remaining headroom

Based on USGS 2020 water-use data and EPA-standard cooling intensity constants. Not a substitute for site-specific water rights analysis.

Editorial analysis

Understanding San Francisco County’s Water

Drinking Water Quality Overview

EPA SDWIS

San Francisco County earns an A grade for drinking water quality, scoring 86.0 out of 100. EPA's Safe Drinking Water Information System (SDWIS) records zero health-based violations over the past five years — a strong compliance signal for a mid-sized county.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). A notable 28.1% of assessed waterways carry an impairment designation (9 of 32 water bodies) across San Francisco County's watersheds. The leading impairment causes are chlordane and dieldrin. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. San Francisco County has moderate coverage with 31 active monitoring sites with 18,429 recent measurements on record. Predominant monitoring categories include microbiological and nutrient. More monitoring sites generally indicate greater scientific attention to local water conditions — and provide the baseline data that regulators use to set future impairment listings.

Editorial advisory

What the data suggests for San Francisco County

Water Verdict

San Francisco County receives an excellent water quality assessment with a grade of A and a score of 86.0 out of 100. The water supply meets or exceeds federal safety standards, and residents can generally drink tap water with confidence.

Violation Context

San Francisco County has recorded zero health-based violations, indicating no recent health-based violations in the reporting period. The violation rate is zero per 100,000 people served, which is the best possible outcome.

Consumer Guidance

The EPA compliance record for San Francisco County shows no recent health-based violations. No health-based violations have been recorded, placing San Francisco County in the top tier for drinking-water safety. San Francisco County's drinking-water compliance score is 86.0 out of 100. As a routine precaution, requesting your utility's annual Consumer Confidence Report each July gives you a full list of detected contaminants and their treatment levels. With 31 active water-quality monitoring sites in San Francisco County, data coverage is strong.

Regional Context

San Francisco County has better water quality than the average county in California. Its water score is 41.4 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Advisory text summarizes county-level public records and is not a replacement for your utility's current Consumer Confidence Report or direct local notices.

Contaminants & Resources

Key issues flagged in San Francisco County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Chlordane

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 2

    Dieldrin

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 3

    Mercury

    Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for San Francisco County

EPA How's My Waterway

Interactive watershed health data for San Francisco County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for San Francisco County

Consumer Confidence Reports (CA)

Annual water quality reports from utilities in California

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

28.1%

9 of 32 assessed

Some impairment

Top Impairment Causes

  • 1

    CHLORDANE

  • 2

    DIELDRIN

  • 3

    MERCURY

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state; counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

31

Active in the past 5 years

Measurements Recorded

18K

18,429 total readings

Most Measured

  • Microbiological
  • Nutrient
  • Physical

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

Free tool

Estimate Your Water Costs

Water Cost Estimate

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for San Francisco County:B — Good

Minor violations; waterways mostly healthy.

Estimates use the national average residential water rate ($0.0068/gal, EPA/AWWA 2023) and EPA WaterSense per-person consumption baseline (75 gal/person/day). Actual bills vary by utility, usage tier, and local infrastructure fees. For informational purposes only.

Try the full calculator →

San Francisco County has good water quality

Learn about water restrictions and conservation in your area.

Water Restrictions →

Frequently Asked Questions

What is the water quality in San Francisco County, California?
San Francisco County, California has a drinking-water quality grade of A with a score of 86.0/100, based on EPA SDWIS compliance data. The county has 0 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and streamflow snapshots are reported separately on this page.
Are there any water violations in San Francisco County?
San Francisco County has 0 health-based drinking water violations recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Zero violations is an excellent record indicating consistent compliance with federal drinking water standards.
How healthy are the watersheds in San Francisco County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 28.1% of San Francisco County's 32 assessed water bodies are classified as impaired (9 impaired). The top reported causes are CHLORDANE, DIELDRIN, MERCURY. Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in San Francisco County?
EPA's Water Quality Portal records 18,429 measurements from 31 monitoring sites in San Francisco County over the past five years. The most frequently measured characteristic groups are Microbiological, Nutrient, Physical. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
How does San Francisco County water compare to the California average?
San Francisco County's SDWIS water quality score of 86.0/100 is higher than the California state average of 44.6. The average water quality grade across California is D, based on data from 58 counties with available SDWIS data.
Is tap water safe to drink in San Francisco County?
Based on EPA SDWIS data, San Francisco County has a water quality grade of A (86.0/100). This indicates good to excellent water quality with strong SDWIS compliance. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Does San Francisco County have clean drinking water?
San Francisco County has 0 health-based drinking water violations according to EPA records. With a water quality score of 86.0/100 and grade A, the county's drinking water meets EPA standards with no recorded health violations. Note: drinking-water compliance speaks to the public water system, not necessarily to the watershed itself — check the Watershed Health zone for ATTAINS §303(d) data.
How does San Francisco County rank for water quality in California?
San Francisco County ranks #1 out of 58 counties in California by SDWIS water quality score (1 = best). With a score of 86.0/100, it falls in the top third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Alameda County

California

A

71.9

Water score

Orange County

California

A

71.5

Water score

Placer County

California

A

69.8

Water score

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments, state-reported and EPA-finalized.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP), federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

By Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

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