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States → Guam

State profile · EPA SDWIS + UCMR5

Guam Drinking Water Quality

8 public water systems serve 327,417 people across Guam, with every Safe Drinking Water Act violation and UCMR5 PFAS result on record.

8
Water systems
203
Total violations
100%
Systems w/ a violation
60%
PFAS detection rate

The verdict

Across Guam, 8 of 8 water systems (100.0%) carry at least one EPA violation, and 3 of 5 UCMR5-tested systems show PFAS.

203
Total EPA violations on record
46%
Health-based (MCL / treatment)
100.0%
Systems with ≥1 violation
60%
UCMR5 PFAS detection rate
Water Systems
8
Total Violations
203
Violation Rate
100%
PFAS Detection
60%
3 of 5 tested

Violation Composition

How Guam's 203 violations break down by type, per EPA SDWIS classification.

Health-based (94) Monitoring/Reporting (109)
Metric Value Share
Public water systems8-
Population served327,417-
Total violations203100%
Health-based violations9446.3%
Systems with violations8100.0%
PFAS detection rate3 of 560%

Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement. Monitoring/reporting violations indicate procedural issues (missed tests, late reports) - not necessarily a contamination event.

Largest Water Systems

Gwa Northern Water System
Mangilao, GU · 139,207 served
30 violations
Guam International Airport Authority
Tamuning, GU · 138,336 served
2 violations
Gwa Central Water System
Mangilao, GU · 21,398 served
106 violations
U.S. Navy Water System
Fp, GU · 12,780 served
23 violations
Andersen Air Force Base Water System
Apo Ap, GU · 7,700 served
10 violations
Gwa Southern Water System
Mangilao, GU · 5,801 served
24 violations
Guam Regional Medical City
Dededo, GU · 1,100 served
3 violations
Guam Plaza Resort Water System
Tumon, GU · 1,095 served
5 violations

Most Violations

#1 Gwa Central Water System Mangilao
106
#2 Gwa Northern Water System Mangilao
30
#3 Gwa Southern Water System Mangilao
24
#4 U.S. Navy Water System Fp
23
#5 Andersen Air Force Base Water System Apo Ap
10
#6 Guam Plaza Resort Water System Tumon
5
#7 Guam Regional Medical City Dededo
3
#8 Guam International Airport Authority Tamuning
2

Counties in Guam

Guam
8 systems · 327,417 served · 203 violations
View all 8 systems in Guam →

Drinking Water Guides

Is Your Tap Water Safe?

How to interpret water quality reports and know when to take action.
PFAS in Drinking Water

What forever chemicals are, EPA testing results, and 2024 standards.
Check Your Water System

Step-by-step guide to finding and understanding your local water data.

Frequently Asked Questions

How many water systems are in Guam? ▼
Guam has 8 public water systems serving approximately 327,417 people. These include community water systems, non-transient non-community systems, and transient non-community systems regulated under the Safe Drinking Water Act.
How many drinking water violations are in Guam? ▼
Guam has 203 total drinking water violations on record, with 94 classified as health-based violations. 100.0% of water systems in the state have at least one violation.
Has PFAS been found in Guam drinking water? ▼
Of 5 water systems tested for PFAS in Guam, 3 had PFAS detected, a 60% detection rate. PFAS are persistent "forever chemicals" that do not break down in the environment.
What is the violation rate for Guam water systems? ▼
Guam's violation rate is 100%. This measures the percentage of public water systems that have at least one recorded violation in the EPA SDWIS database, including both health-based and monitoring/reporting violations.
Where does this Guam water data come from? ▼
All drinking water data comes from the EPA Safe Drinking Water Information System (SDWIS) and the UCMR5 PFAS monitoring program. SDWIS is the federal database that tracks compliance for all public water systems regulated under the Safe Drinking Water Act.

Data Sources & Methodology

Drinking water violation data from the EPA Safe Drinking Water Information System (SDWIS). PFAS testing data from the UCMR5 monitoring program. SDWIS tracks all public water systems regulated under the Safe Drinking Water Act.

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

Related

All states → | Most violations → | Compare counties →
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 page draws directly on 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.