Is Tamuning, GU Tap Water Safe? Quality & Contaminants

What was found in Tamuning's water

The level at the city's main supplier, the highest level anywhere in the city, the EPA limit for each, and where every figure comes from.

Contaminant	Level vs EPA limit	Suppliers	Source
6:2 Fts	0.1482 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
PFOS	0.1350 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
PFHXS	0.0800 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
Pfpea	0.0475 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
Pfhxa	0.0371 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
PFBS	0.0349 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
Pfhpa	0.0185 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
PFOA	0.0183 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
Pfba	0.0181 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
Pfpes	0.0099 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
8:2 Fts	0.0075 µg/L No EPA limit set Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2024	1/1	UCMR-5
Lead	0.0017 mg/L 11% of the EPA limit 0.0150 mg/L Main supplier: GWA NORTHERN WATER SYSTEM · 139,207 people · 2025	1/1	LCR

Each bar shows the measured level as a share of the EPA limit: green is well under, amber is close to it, red is over. For lead and copper the limit applies to exactly the 90th-percentile figure shown, so red there means a real exceedance. For everything else the limit applies to a running annual average while the figure is the 95th percentile of the system's samples — over 100% is worth reading, but is not by itself a violation. Formal violations are listed separately. These are the utilities' own EPA-reported results, not a city-wide average. A detection means the lab measured the substance — it isn't the same as exceeding a legal limit. Hover a source tag to see the EPA program and years behind each figure.

Water suppliers serving Tamuning

Supplier	Population served
GWA NORTHERN WATER SYSTEM	139,207

Frequently asked questions about Tamuning tap water

Is Tamuning tap water safe to drink?

EPA testing detected 12 contaminants in the water serving Tamuning. A detection isn't the same as a violation — most detected levels are within federal limits. Check the level and source for each contaminant above, and your utility's annual Consumer Confidence Report for the official compliance status.

How many water suppliers serve Tamuning?

1 public water supplier report drinking-water monitoring for Tamuning, GU to the EPA. Each is listed above with its population served.

What contaminants are in Tamuning's water?

The contaminants EPA monitoring detected in Tamuning include 6:2 Fts, PFOS, PFHXS, Pfpea, Pfhxa. The full list, with the level at the main supplier and the data source, is in the table above.

Where does this data come from?

Every figure is official EPA drinking-water monitoring — the Lead & Copper Rule, the UCMR-5 nationwide testing program, and the EPA Six-Year Review — not our own testing. Each number is labelled with its source and period.