PFAS above a 2024 limit
MCL1of 21 cities
Cities whose system reported a PFAS above its federal limit.
PFOS in Idaho →State water report
Idaho Water Quality: 21 Cities Ranked by the Records
Water quality across 21 cities in Idaho, drawn from EPA drinking-water records. Each city page shows the measured contaminants and a reproducible Purity Score.
Finding by finding
What Idaho's records show
Counts of cities whose serving system reported each result. There is no statewide score: PurityMap does not average local records into a statewide safety verdict. 3 cities have a past health-based violation on record.
Lead detected
Action level14of 21 cities
90th-percentile lead above zero.
Lead across Idaho →Lead above action level
Action level0of 21 cities
No city on record above 15 µg/L.
How lead is measured →Nitrate above the MCL
MCL0of 21 cities
Cities whose system reported nitrate above 10 mg/L.
About nitrate →Hard or very hard
No federal limit0of 21 cities
Above 120 mg/L as CaCO₃ (7 gpg) on the USGS scale, of 1 cities with a hardness value.
About hard water →City rankings
Idaho cities ranked by the records
Highest first. A summary of each serving system’s record, not a safety verdict.
- 1CaldwellCALDWELL CITY OF · ID3140013Report →
- 2Twin FallsTWIN FALLS CITY OF · ID5420058Report →
- 3KunaKUNA CITY OF · ID4010085Report →
- 4AmmonAMMON CITY OF · ID7100004Report →
- 5RathdrumRATHDRUM CITY OF · ID1280152Report →
- 6LewistonLEWISTON CITY OF · ID2350014Report →
- 7NampaNAMPA CITY OF · ID3140080Report →
- 8Coeur D'AleneCOEUR D ALENE CITY OF · ID1280053Report →
- 9Post FallsPOST FALLS CITY OF · ID1280147Report →
- 10ChubbuckCHUBBUCK CITY OF · ID6030008Report →
Showing the top 10 of 21 scored cities.
Highest detected PFOS result first. The tick marks the 4.0 ng/L federal MCL.
- 1Garden CityGARDEN CITY WATER AND SEWER SYSTEM · ID401006628.2 ng/LReport →
Showing the top 1 of 1 cities with a pfas result.
Highest 90th-percentile result first. The tick marks the 15 µg/L action level.
- 1PocatelloPOCATELLO CITY OF · ID60300435 µg/LReport →
- 2MoscowMOSCOW WATER DEPT · ID22900234 µg/LReport →
- 3Idaho FallsIDAHO FALLS CITY OF · ID71000393 µg/LReport →
- 4BlackfootBLACKFOOT CITY OF · ID60600073 µg/LReport →
- 5JeromeJEROME CITY OF · ID52700113 µg/LReport →
- 6SandpointSANDPOINT PUBLIC WORKS DEPT · ID10901213 µg/LReport →
- 7BoiseVEOLIA WATER IDAHO · ID40100162 µg/LReport →
- 8NampaNAMPA CITY OF · ID31400802 µg/LReport →
- 9Coeur D'AleneCOEUR D ALENE CITY OF · ID12800532 µg/LReport →
- 10RexburgREXBURG CITY OF · ID73300222 µg/LReport →
Showing the top 10 of 14 cities with a lead result.
Hardest first, from utility reports on file. An aesthetic measure with no federal limit.
See all 21 in the table
21 cities, highest Purity Score first
- CALDWELL CITY OF · PWSID ID3140013 · Purity Score 100/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detectedNot detected
- TWIN FALLS CITY OF · PWSID ID5420058 · Purity Score 100/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detectedNot detected
- 3KunaKUNA CITY OF · PWSID ID4010085 · Purity Score 100/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detectedNot detected
- AMMON CITY OF · PWSID ID7100004 · Purity Score 100/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detectedNot detected
- RATHDRUM CITY OF · PWSID ID1280152 · Purity Score 100/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelPFAS detected, none above a limitDetected
- LEWISTON CITY OF · PWSID ID2350014 · Purity Score 99/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelPFAS detected, none above a limit; lead 1 µg/LDetected
- NAMPA CITY OF · PWSID ID3140080 · Purity Score 98/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 2 µg/LDetected
- COEUR D ALENE CITY OF · PWSID ID1280053 · Purity Score 98/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelPFPeA 3.4 ng/L detected, no federal or state limit; lead 2 µg/LDetected
- POST FALLS CITY OF · PWSID ID1280147 · Purity Score 98/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 1 µg/LDetected
- 10ChubbuckCHUBBUCK CITY OF · PWSID ID6030008 · Purity Score 98/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 2 µg/LDetected
- MIDDLETON CITY OF · PWSID ID3140074 · Purity Score 98/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 2 µg/LDetected
- IDAHO FALLS CITY OF · PWSID ID7100039 · Purity Score 97/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 3 µg/LDetected
- 13RexburgREXBURG CITY OF · PWSID ID7330022 · Purity Score 97/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelPast e. coli violation on recordDetected
- 14JeromeJEROME CITY OF · PWSID ID5270011 · Purity Score 97/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 3 µg/LDetected
- 15MoscowMOSCOW WATER DEPT · PWSID ID2290023 · Purity Score 95/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 4 µg/LDetected
- SANDPOINT PUBLIC WORKS DEPT · PWSID ID1090121 · Purity Score 95/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detected; lead 3 µg/LDetected
- BLACKFOOT CITY OF · PWSID ID6060007 · Purity Score 94/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelPast e. coli violation on recordDetected
- POCATELLO CITY OF · PWSID ID6030043 · Purity Score 93/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelPast nitrate violation on recordDetected
- MOUNTAIN HOME, CITY OF · PWSID ID4200032 · Purity Score 93/100 (Excellent) · Confidence: moderate · Assessed at the water-system levelNo PFAS detectedNot detected
- 20BoiseVEOLIA WATER IDAHO · PWSID ID4010016 · Purity Score 82/100 (Good) · Confidence: high · Assessed at the water-system levelNo PFAS detected; lead 2 µg/LDetected
- GARDEN CITY WATER AND SEWER SYSTEM · PWSID ID4010066 · Purity Score 57/100 (Fair) · Confidence: moderate · Assessed at the water-system levelPFOS 28.2 ng/L, 7× the EPA limit (+1 more PFAS above)Above reference
Showing 12 of 21.
Ranked by the Purity Score of each city's main water system, highest first. Scores belong to water systems; there is no state 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. See how Idaho compares with other states.
By contaminant
PFAS, lead and hard water in Idaho
PFAS
MCLHighest detected PFOS result, by city.
- Garden City28.2 ng/L
| 4.0 ng/L federal MCL · 1 city above it
Lead
Action level90th-percentile result, by city.
- Pocatello5 µg/L
- Moscow4 µg/L
- Idaho Falls3 µg/L
- Blackfoot3 µg/L
- Jerome3 µg/L
| 15 µg/L action level · none above
Hard water
No federal limitReported hardness, by city.
- Boise6.3 gpg
Aesthetic measure · USGS scale
Counties
13 counties with city reportsIdaho counties
- Ada County3 cities
- Canyon County3 cities
- Kootenai County3 cities
- Bannock County1 city
- Bingham County1 city
- Bonner County1 city
- Bonneville County1 city
- Elmore County1 city
- Jerome County1 city
- Latah County1 city
Show all 13 counties
- Madison County1 city
- Nez Perce County1 city
- Twin Falls County1 city
Suppliers
Largest water systems
- VEOLIA WATER IDAHOBoise · ID4010016 · 264,978 served
- NAMPA CITY OFNampa · ID3140080 · 100,200 served
- CALDWELL CITY OFCaldwell · ID3140013 · 74,000 served
- IDAHO FALLS CITY OFIdaho Falls · ID7100039 · 69,450 served
- POCATELLO CITY OFPocatello · ID6030043 · 58,231 served
- TWIN FALLS CITY OFTwin Falls · ID5420058 · 56,121 served
Next step
State patterns can’t tell you what reaches your tap.
Learn
Learn your supplier
Resolve your address to the one public water system that serves it.
Find my water →Test
Test your own tap
Plumbing inside a building can add lead and change what reaches your glass.
How to test →Solve
Treat by concern
Only after a city report names a finding, match a treatment certified for it.
Treatment options →Questions
Idaho water, frequently asked
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How does Idaho tap water compare across cities?
PurityMap ranks 21 cities in Idaho 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 Caldwell's main water system: CALDWELL CITY OF · PWSID ID3140013 · 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 Idaho cities have PFAS above the federal limit?
1 city of 21 had at least one regulated PFAS (PFOA, PFOS or PFHxS) measured above the 2024 federal limit in EPA's UCMR 5 testing, including Garden City (PFOS 28.2 ng/L). PFAS were detected at any level in 4.
Is there lead in Idaho tap water?
Utilities report lead as a 90th-percentile result from home taps. 14 of 21 Idaho 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.
Have Idaho water systems had drinking-water violations?
3 cities in Idaho have a health-based violation in the federal SDWIS record within about the last ten years. Each city report lists the contaminant, year and whether it was resolved.
Does Idaho have hard water?
Hardness is published in utility water-quality reports for 1 Idaho city on record; the hardest is Boise at 6.3 grains per gallon. Hardness affects scale and appliances; it is not a health finding.
Limits, sources and corrections
A statewide page cannot tell you what reaches a specific address. Water quality varies by supplier, sampling period and household plumbing; open a city report for the evidence behind a local result.
Sources: EPA UCMR 5 (PFAS, 2024), SDWIS Lead and Copper Rule 90th-percentile results and health-based violations, and utility Consumer Confidence Reports where on file. Every city report links its dated source records.
Updated 2026-09-16. How PurityMap analyzes water data · Report an error