Is the tap water in ASAN, GU safe to drink?

ASAN's tap water receives a grade of A (98/100) from TapWaterSafety.org. No major concerns are flagged in current data. Grades are based on EPA SDWIS, EPA ECHO, EWG Tap Water Database, and the utility's published Consumer Confidence Report.

What contaminants are in ASAN tap water?

Public data sources identify the following contaminants in ASAN's water supply: . Levels and comparison to EWG health guidelines are listed on the full city page.

Which water utility serves ASAN?

ASAN is served by GWA NORTHERN WATER SYSTEM. GWA NORTHERN WATER SYSTEM serves approximately 139,207 residents.

Tap Water Quality Report

Tap water quality in ASAN, GU

Served by GWA NORTHERN WATER SYSTEM. 139,207 residents.

Average score 98/100

Utilities 1

Population 139,207

98/100

Excellent

ⓘ How did we get this rating?

Quick answer

Tap water in ASAN, GU receives a grade of A (98/100) from TapWaterSafety.org. It's served by GWA NORTHERN WATER SYSTEM. Data sources: EPA SDWIS, EPA ECHO, EWG Tap Water Database.

Data sources for this grade: utilities.csv EWG Tap Water Database ⓘ How did we get this rating?

EPA compliance record

Official U.S. EPA records for GWA NORTHERN WATER SYSTEM (system ID GU0000006) for the last 3 years. Checked 2026-10-07.

No EPA violations in the last 3 years.

0 of 12quarters with a violation

Nolead above EPA action level

07/03/2024last state inspection

Source: U.S. EPA Enforcement and Compliance History Online (ECHO), from the Safe Drinking Water Information System. See EPA's full report.

Recommended filters for ASAN

Filters matched to the specific contaminants in ASAN's water supply.

Carbon block filter certified to NSF/ANSI 42 + 53

$180-$599

A certified carbon block filter handles most baseline water quality concerns.

Aquasana AQ-5300 Under-Sink Filter

$180-$240 NSF 42, 53, 401, 372

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AquaTru Countertop Reverse Osmosis

$449-$599 NSF 42, 53, 58, 401, 372

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Disclosure: TapWaterSafety earns a commission from purchases made through these links. This does not influence our scoring methodology or filter selection.

Treatment plant contact info

For service issues, water quality concerns, or to request a Consumer Confidence Report from GWA NORTHERN WATER SYSTEM.

General Contact

AddressGloria B. Nelson Public Service Building, MANGILAO, GU 96913

Main phone671-300-6845

Emailmcbordallo@guamwaterworks.org

Treatment Plant

FacilityTP FOR WELL A-6

ZIP codes served

ASAN's public water systems serve the following ZIP codes: