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Updated 2026-10-15
County water report

Ada County Water Quality: 5 Cities Ranked by the Records

Ada County, Idaho: 5 city reports built from EPA and utility records. A county has many suppliers; each city shows the system that serves it.

Find my systemOpen on the mapPrivate wells in Ada County
Across the county's systems

Highest result for each contaminant

One row per contaminant: the highest result any system in the county reported, against its limit. Open a row for the systems behind it.

LithiumDetected in 5 systems10 µg/L EPA health reference level (screening, not a legal limit) · US EPAHighest99.5 µg/L
Perfluorooctanesulfonic acid (PFOS)Detected in 2 systems of 5 tested4.0 ng/L federal MCL (2024) · US EPAHighest28.2 ng/L
Perfluorohexanesulfonic acid (PFHxS)Detected in 2 systems of 5 tested10 ng/L federal MCL (2024) · US EPAHighest25.4 ng/L
ArsenicDetected in 1 system0.010 mg/L · US EPAHighest0.0086 mg/L
Perfluorononanoic acid (PFNA)Detected in 1 system of 5 tested10 ng/L federal MCL (2024) · US EPAHighest8.2 ng/L
Haloacetic acids (HAA5)Detected in 1 system60 ppb federal MCL · US EPAHighest41.8 ppb
NitrateDetected in 1 system10 mg/L · US EPAHighest5.6 mg/L
Total trihalomethanes (TTHM)Detected in 1 system80 ppb federal MCL · US EPAHighest43.8 ppb
8 more contaminants detectedShow
CopperDetected in 1 system1.3 mg/L (action level) · US EPAHighest0.5 mg/L
Lead (90th percentile)Detected in 4 systems of 5 tested15 µg/L federal action level · US EPAHighest3.9 µg/L
FluorideDetected in 1 system4.0 mg/L · US EPAHighest0.9 mg/L
Perfluorobutanesulfonic acid (PFBS)Detected in 1 system of 5 tested2,000 ng/L EPA health advisory (screening, not a legal limit) · US EPAHighest6.7 ng/L
Perfluorohexanoic acid (PFHxA)Detected in 1 system of 5 tested400,000 ng/L Michigan EGLE state MCL (strictest US state) · Michigan EGLEHighest6.5 ng/L
Water hardnessDetected in 1 systemAesthetic, no federal health limit · USGSHighest6.3 gpg
Perfluoropentanesulfonic acid (PFPeS)Detected in 1 system of 5 testedNo federal or state limit; shown for transparencyHighest4.4 ng/L
Perfluoropentanoic acid (PFPeA)Detected in 1 system of 5 testedNo federal or state limit; shown for transparencyHighest4.8 ng/L
22 PFAS tested, none detected in any systemShow

Tested in these 5 systems: GARDEN CITY WATER AND SEWER SYSTEM, KUNA CITY OF, MERIDIAN WATER DEPT, STAR SEWER AND WATER DIST WATER SYSTEM, VEOLIA WATER IDAHO

  • 11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS)
  • 1H, 1H, 2H, 2H-perfluorodecane sulfonic acid (8:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorohexane sulfonic acid (4:2 FTS)
  • 1H, 1H, 2H, 2H-perfluorooctane sulfonic acid (6:2 FTS)
  • 4,8-Dioxa-3H-perfluorononanoic acid (ADONA)
  • 9-Chlorohexadecafluoro-3-oxanone-1-sulfonic acid (9Cl-PF3ONS)
  • Hexafluoropropylene oxide dimer acid (HFPO-DA) (GenX chemicals)
  • N-ethyl perfluorooctanesulfonamidoacetic acid (NEtFOSAA)
  • N-methyl perfluorooctanesulfonamidoacetic acid (NMeFOSAA)
  • Nonafluoro-3,6-dioxaheptanoic acid (NFDHA)
  • Perfluoro (2-ethoxyethane) sulfonic acid (PFEESA)
  • Perfluoro-3-methoxypropanoic acid (PFMPA)
  • Perfluoro-4-methoxybutanoic acid (PFMBA)
  • Perfluorobutanoic acid (PFBA)
  • Perfluorodecanoic acid (PFDA)
  • Perfluorododecanoic acid (PFDoA)
  • Perfluoroheptanesulfonic acid (PFHpS)
  • Perfluoroheptanoic acid (PFHpA)
  • Perfluorooctanoic acid (PFOA)
  • Perfluorotetradecanoic acid (PFTA)
  • Perfluorotridecanoic acid (PFTrDA)
  • Perfluoroundecanoic acid (PFUnA)
5 cities

Cities ranked by the records

Showing 5 of 5 cities · scores are system-level, not tap tests

Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no county score. The score is computed only from contaminants measured in the published EPA record, so this ranks the record, not which city's water is safest. How the score works.

PFAS in Ada County2 of 5 city reports had a PFAS sample above a 2024 EPA limit
  1. Garden City28.2 ng/L
  2. Meridian4.9 ng/L
4.0 ng/L federal MCL · PFOS, ng/LPFAS in Idaho
Lead

0of 5 cities above the 15 µg/L action level

Based on each system's 90th-percentile result. Lead from household plumbing isn't in this record.

Lead in Idaho
Hard water

1city reports hardness · Boise, 6.3 gpg

None above 7 gpg, the USGS threshold for hard water. An aesthetic measure with no federal health limit.

Hard water explained
Who supplies the county

Largest water systems

  1. BoiseVEOLIA WATER IDAHO · ID4010016
    264,978 served
  2. MeridianMERIDIAN WATER DEPT · ID4010097
    152,070 served
  3. KunaKUNA CITY OF · ID4010085
    32,038 served
  4. StarSTAR SEWER AND WATER DIST WATER SYSTEM · ID4010220
    14,000 served
  5. Garden CityGARDEN CITY WATER AND SEWER SYSTEM · ID4010066
    12,500 served
Questions

Frequently asked

How does Ada County tap water compare across cities?

PurityMap ranks 5 cities in Ada County by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Kuna's main water system: KUNA CITY OF · PWSID ID4010085 · Purity Score 100 (Excellent) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.

How many Ada County cities had a PFAS sample above a 2024 EPA limit?

2 of 5 Ada County city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Garden City (PFOS 28.2 ng/L), Meridian (PFOS 4.9 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 2.

Is there lead in Ada County tap water?

Utilities report lead as a 90th-percentile result from home taps. 4 of 5 Ada County cities reported a value above zero, and none was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.

Does Ada County have hard water?

Hardness is published in utility water-quality reports for 1 Ada County city on record; the hardest is Boise at 6.3 grains per gallon. Hardness affects scale and appliances; it is not a health finding.

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