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Tap water quality report

Issaquah, WA

EPA monitoring detected 16 contaminants across the 4 water suppliers serving Issaquah. A detection doesn't automatically mean the water is unsafe — see the level at the main supplier for each below, with its EPA source and period.

4
water suppliers
43,739
people served
16
contaminants found
Washington rankings Lead in Washington PFAS in Washington

What was found in Issaquah'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.

ContaminantLevel vs EPA limitSuppliersSource
Nitrate
655.5 µg/L 6.6%
of the EPA limit 10000 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
Highest in the city: 1700 µg/L — ISSAQUAH VALLEY WATER ASSN #1 · 80 people · 2018
3/4 SYR4
Nitrate-Nitrite
535 µg/L 5.4%
of the EPA limit 10000 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2016
Highest in the city: 1700 µg/L — ISSAQUAH VALLEY WATER ASSN #1 · 80 people · 2018
3/4 SYR4
TTHM
49.44 µg/L 62%
of the EPA limit 80 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Chloroform
46.44 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Total Haloacetic Acids (HAA5)
37.87 µg/L 63%
of the EPA limit 60 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Copper
5 µg/L 0.4%
of the EPA limit 1300 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2016
Highest in the city: 33 µg/L — ISSAQUAH VALLEY WATER ASSN #1 · 80 people · 2016
2/4 SYR4
Trichloroacetic Acid
23.775 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Dichloroacetic Acid
17.14 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Barium
11.95 µg/L 0.6%
of the EPA limit 2000 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2016
1/4 SYR4
Arsenic
8.1 µg/L 81%
of the EPA limit 10 µg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2016
2/4 SYR4
Monochloroacetic Acid
3.305 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Bromodichloromethane
3.2 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Dibromochloromethane
2.48 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Lead
1.7 µg/L 11%
of the EPA limit 15 µg/L
Highest in the city: ISSAQUAH VALLEY WATER ASSN #1 · 80 people · 2016
1/4 SYR4
Bromoform
0.5000 µg/L
No EPA limit set
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2019
1/4 SYR4
Lead
0.0010 mg/L 6.7%
of the EPA limit 0.0150 mg/L
Main supplier: ISSAQUAH WATER SYSTEM · 43,584 people · 2022
Highest in the city: 0.0018 mg/L — ALPINE MOBILE MANOR · 45 people · 2025
4/4 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 Issaquah

SupplierPopulation served
ISSAQUAH WATER SYSTEM 43,584
ISSAQUAH VALLEY WATER ASSN #1 80
ALPINE MOBILE MANOR 45
TIGER MTN TRACTS 30

Frequently asked questions about Issaquah tap water

Is Issaquah tap water safe to drink?

EPA testing detected 16 contaminants in the water serving Issaquah. 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 Issaquah?

4 public water suppliers report drinking-water monitoring for Issaquah, Washington to the EPA. Each is listed above with its population served.

What contaminants are in Issaquah's water?

The contaminants EPA monitoring detected in Issaquah include Nitrate, Nitrate-Nitrite, TTHM, Chloroform, Total Haloacetic Acids (HAA5). 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.