PlainWater
States → Puerto Rico

Community Water System · PWS PR0003303

San Sebastian

San Sebastian, Puerto Rico 00685 - drinking water served from surface water sources to 24,449 people, tracked in EPA SDWIS and UCMR5.

24,449
People served
250
EPA violations
128
Health-based
No PFAS
UCMR5 result

The verdict

EPA records 250 drinking-water violations at San Sebastian, 51% of them health-based - below the Puerto Rico per-system average.

250
Total EPA violations on record
51%
Health-based (MCL / treatment failure)
24,449
People served by this system
0
PFAS compounds detected (UCMR5)

Water Quality Snapshot: San Sebastian

San Sebastian is a local-owned community water system that delivers drinking water to 24,449 residents in San Sebastian, Puerto Rico (San Sebastian Municipio County) through 9,157 service connections. Its water is drawn from surface water sources. EPA's Safe Drinking Water Information System records 250 total violations for this system , of which 128 (51%) are health-based, meaning a contaminant exceeded an EPA Maximum Contaminant Level or a required treatment technique failed. A further 100 monitoring and reporting violations are on file. The most recent violation on record dates to 2020.

The most frequently cited contaminant at this system is Total Haloacetic Acids (HAA5), recorded in 39 violations (MCL, health-based). This system was sampled under EPA's UCMR5 PFAS monitoring program and no PFAS compounds were detected above the minimum reporting level.

Across Puerto Rico, EPA tracks 458 public water systems serving 3,328,141 people, with 164,144 cumulative violations and 34,657 health-based violations on record. About 100% of systems in the state carry at least one violation, and state-wide the average per system is 358.4 violations. Statewide, 40 of 99 UCMR5-tested systems have reported PFAS detections (40.4%).

San Sebastian's 250 violations sit below the Puerto Rico average.

All figures above are sourced directly from EPA SDWIS and UCMR5 public data releases and are updated as EPA publishes new reporting cycles.

Population Served
24,449
Total Violations
250
Health-Based Violations
128
Water Source
Surface Water

System Details

System Type
Community
Owner Type
Local
Connections
9,157
County
San Sebastian Municipio
School/Daycare
No
MCL Violations
64
Monitoring Violations
100
Treatment Tech Violations
64

Violation History

Contaminant violations recorded by EPA.

Contaminant Category Count Latest
Total Haloacetic Acids (HAA5) MCL 39 2020
Surface Water Treatment Rule TT 38 2001
Interim Enhanced Surface Water Treatment Rule TT 17 2011
Cryptosporidium MR 17 2018
TTHM MCL 17 2016
Turbidity MR 15 2018
E. COLI MR 15 2018
Coliform (TCR) MR 9 2013
CARBON, TOTAL TT 9 2015
Coliform (TCR) MCL 8 2016
Lead and Copper Rule MR 7 2016
Consumer Confidence Rule Other 4 2020
OXAMYL MR 2 2015
Chromium MR 2 1984
Mercury MR 2 1984
Nitrate MR 2 1984
Arsenic MR 2 1984
Selenium MR 2 1984
Cadmium MR 2 1984
Fluoride MR 2 1984
Nitrite MR 2 2005
Barium MR 2 1984
Carbofuran MR 2 2015
TTHM MR 1 2005
ETHYLENE DIBROMIDE MR 1 2005
Chlordane MR 1 2009
Endrin MR 1 2009
BHC-GAMMA MR 1 2009
Heptachlor epoxide MR 1 2009
HEXACHLOROBENZENE MR 1 2009

PFAS Testing Results (UCMR5)

Results from EPA's Fifth Unregulated Contaminant Monitoring Rule. 0 of 116 samples detected PFAS.

Contaminant Date Result MRL Status
PFMBA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
8:2 FTS 9/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFDoA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFDA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpS 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeS 9/26/2023 <4.00 ppt 4.00 ppt Not Detected
PFEESA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFMPA 9/26/2023 <4.00 ppt 4.00 ppt Not Detected
PFHxS 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFUnA 9/26/2023 <2.00 ppt 2.00 ppt Not Detected
PFHpA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFHxA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFBS 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
6:2 FTS 9/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFOA 9/26/2023 <4.00 ppt 4.00 ppt Not Detected
PFOS 9/26/2023 <4.00 ppt 4.00 ppt Not Detected
NFDHA 9/26/2023 <20.00 ppt 20.00 ppt Not Detected
PFNA 9/26/2023 <4.00 ppt 4.00 ppt Not Detected
4:2 FTS 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
ADONA 9/26/2023 <3.00 ppt 3.00 ppt Not Detected
PFBA 9/26/2023 <5.00 ppt 5.00 ppt Not Detected
11Cl-PF3OUdS 9/26/2023 <5.00 ppt 5.00 ppt Not Detected
9Cl-PF3ONS 9/26/2023 <2.00 ppt 2.00 ppt Not Detected
HFPO-DA 9/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFTrDA 9/26/2023 <7.00 ppt 7.00 ppt Not Detected
NEtFOSAA 9/26/2023 <5.00 ppt 5.00 ppt Not Detected
PFTA 9/26/2023 <8.00 ppt 8.00 ppt Not Detected
NMeFOSAA 9/26/2023 <6.00 ppt 6.00 ppt Not Detected
PFBS 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpS 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
HFPO-DA 6/27/2023 <5.00 ppt 5.00 ppt Not Detected
11Cl-PF3OUdS 6/27/2023 <5.00 ppt 5.00 ppt Not Detected
NFDHA 6/27/2023 <20.00 ppt 20.00 ppt Not Detected
PFEESA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFMBA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFPeA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFMPA 6/27/2023 <4.00 ppt 4.00 ppt Not Detected
8:2 FTS 6/27/2023 <5.00 ppt 5.00 ppt Not Detected
4:2 FTS 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
6:2 FTS 6/27/2023 <5.00 ppt 5.00 ppt Not Detected
9Cl-PF3ONS 6/27/2023 <2.00 ppt 2.00 ppt Not Detected
ADONA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFHpA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFUnA 6/27/2023 <2.00 ppt 2.00 ppt Not Detected
PFHxA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFDoA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFDA 6/27/2023 <3.00 ppt 3.00 ppt Not Detected
PFOA 6/27/2023 <4.00 ppt 4.00 ppt Not Detected
PFOS 6/27/2023 <4.00 ppt 4.00 ppt Not Detected

Verify This Water System

The figures above are aggregated from EPA's public databases. To verify the underlying records, or to file a complaint, request a Consumer Confidence Report, or check current monitoring status, go directly to the federal and state regulators that enforce the Safe Drinking Water Act for San Sebastian.

Federal Source of Truth

EPA SDWIS, Federal Reports

EPA's Safe Drinking Water Information System (SDWIS) holds the federal compliance record for every regulated public water system. Open the system-level report by PWS ID:

View PWS ID PR0003303 on SDWIS

Source: EPA SDWIS Federal Reports Search

State Regulator

Puerto Rico Drinking Water Authority

Puerto Rico's primacy agency administers the Safe Drinking Water Act locally. Search EPA SDWIS for the current state contact, or use the state's public health or environment department portal.

Find PR regulator via EPA SDWIS

Violation Timeline

Each row links to the EPA SDWIS public record for verification. Cross-reference the contaminant code on EPA's federal report to see violation dates, return-to-compliance status, and enforcement actions.

Year (latest) Contaminant Category Count EPA Record
2020 Total Haloacetic Acids (HAA5) MCL 39 SDWIS / PR0003303 / 2456
2020 Consumer Confidence Rule Other 4 SDWIS / PR0003303 / 7000
2018 Cryptosporidium MR 17 SDWIS / PR0003303 / 3015
2018 Turbidity MR 15 SDWIS / PR0003303 / 0100
2018 E. COLI MR 15 SDWIS / PR0003303 / 3014
2016 TTHM MCL 17 SDWIS / PR0003303 / 2950
2016 Coliform (TCR) MCL 8 SDWIS / PR0003303 / 3100
2016 Lead and Copper Rule MR 7 SDWIS / PR0003303 / 5000
2015 CARBON, TOTAL TT 9 SDWIS / PR0003303 / 2920
2015 OXAMYL MR 2 SDWIS / PR0003303 / 2036
2015 Carbofuran MR 2 SDWIS / PR0003303 / 2046
2013 Coliform (TCR) MR 9 SDWIS / PR0003303 / 3100
2011 Interim Enhanced Surface Water Treatment Rule TT 17 SDWIS / PR0003303 / 0300
2009 Chlordane MR 1 SDWIS / PR0003303 / 2959
2009 Endrin MR 1 SDWIS / PR0003303 / 2005

How San Sebastian Compares

Cross-reference this system's record against state averages and the federal MCL framework for context.

Metric San Sebastian Puerto Rico avg Federal benchmark
Total violations 250 358.4 SDWA compliance, any non-zero count is a recorded breach
Health-based violations 128 75.7 Indicates a contaminant exceeded a federal MCL
PFAS detection None 40.4% EPA final rule (2024): PFOA/PFOS MCL = 4.0 ppt
Population served 24,449 7,267 Sizing context for compliance burden

Sources: EPA SDWIS and EPA National Primary Drinking Water Regulations (40 CFR Part 141). State averages computed across 458 regulated public water systems in Puerto Rico.

Federal MCL reference, Safe Drinking Water Act thresholds ▼
Contaminant Federal MCL / Action Level Note
Lead 0 mg/L (Action Level: 0.015 mg/L) Lead and Copper Rule treatment technique
Arsenic 0.010 mg/L (10 ppb) Health-based MCL since 2006
Total Coliform Treatment technique (RTCR) Indicator organism, monitoring trigger
PFOA / PFOS (PFAS) 4.0 ppt each (final 2024 rule) Compliance deadline 2029 (EPA proposed extending to 2031, not yet final as of May 2026)
Nitrate (as N) 10 mg/L Acute health risk for infants

Frequently Asked Questions

Is San Sebastian water safe to drink? ▼
San Sebastian (PWS ID: PR0003303) has 250 recorded violations in the EPA SDWIS database. No PFAS contamination was detected in UCMR5 testing. This system serves 24,449 people using Surface Water sources.
How many people does San Sebastian serve? ▼
San Sebastian serves 24,449 people in San Sebastian, Puerto Rico. It is a Local-owned system using Surface Water water sources with 9,157 service connections.
What type of violations does San Sebastian have? ▼
San Sebastian has 250 total violations: 128 health-based violations (MCL exceedances or treatment failures), 100 monitoring/reporting violations, and 64 treatment technique violations. Health-based violations indicate contaminant levels exceeded EPA safe limits.
Has PFAS been detected in San Sebastian water? ▼
No. San Sebastian was tested for PFAS under the EPA's UCMR5 monitoring program and no PFAS contamination was detected.
What water source does San Sebastian use? ▼
San Sebastian uses Surface Water as its primary water source. It is classified as a Community Water System (CWS), serving residential populations year-round.
Where does this data come from? ▼
All data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS tracks compliance for all public water systems regulated under the Safe Drinking Water Act.
Data Sources: EPA Safe Drinking Water Information System (SDWIS), Q4 2025. PFAS data from EPA UCMR5 monitoring program (2023-2025). This data is provided for informational purposes only.

Read our methodology - how this data is sourced, computed, and verified.

Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This system's figures are rendered directly from EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.