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Not health advice. Contact your local water utility for concerns.
Data from EPA Water Quality Reports. For official information, contact your water utility or health department.
Water quality scores for 20 cities in Idaho
It depends on your utility. 3 of the 20 Idaho water systems we grade from EPA records have a health-based violation in the last five years; the state averages 90/100 (2 above the national 88). Lowest graded: Blackfoot (C). Highest: Caldwell (A).
Idaho's official certified-lab list, when to test well vs city water, typical lab prices, and how to take a first-draw lead sample.
Across the 20 Idaho water systems we can grade from EPA records, the average score is 90/100 — 2 points above the U.S. national average of 88/100. 60% of graded Idaho cities (12 of 20) score above that national benchmark, and 10 earn a Grade A. 3 cities have at least one health-based EPA violation in the last five years.
The contaminants most commonly flagged in Idaho water systems are nitrates (irrigated agriculture), arsenic (naturally occurring in groundwater) and heavy metals (northern mining legacy). See the full breakdown in our Idaho water quality rankings or compare against the cities with the best water quality in America.
See the top 20 cities with the cleanest, safest drinking water
Complete water quality rankings for every city in Idaho
74,000 residents
69,450 residents
20,285 residents
20,000 residents
6,108 residents
15,842 residents
13,135 residents
26,000 residents
17,338 residents
40,695 residents
100,200 residents
32,038 residents
54,115 residents
264,978 residents
56,121 residents
12,500 residents
58,231 residents
147,340 residents
14,651 residents
13,224 residents
Idaho's water quality is generally good, fed by mountain snowmelt and large aquifer systems, but the state faces localized issues from agriculture, mining legacy in the north, and naturally occurring contaminants. The vast Eastern Snake River Plain Aquifer is one of the most productive in the country and supplies much of southern Idaho.
Across the 20 Idaho cities graded from EPA records, the average water quality score is 90/100. The highest-rated city is Caldwell with a score of 100/100, while Blackfoot has the most room for improvement at 70/100.
Idaho cities average 90/100, but contaminants still vary at the tap and lead can leach from your own household plumbing after the water arrives. A certified filter removes trace contaminants and improves taste — here are two proven picks.
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Southern Idaho relies heavily on the Eastern Snake River Plain Aquifer and the Snake River, supporting both drinking water and extensive irrigation. Boise draws from the Boise River and groundwater. Northern Idaho communities use mountain surface water and aquifers, some affected by the historic Silver Valley mining district.
These contaminants have been detected in various Idaho water systems
The Idaho Department of Environmental Quality (DEQ) administers the Safe Drinking Water Act and oversees source water protection. Idaho monitors nitrate trends in heavily irrigated areas and coordinates on cleanup of the Bunker Hill Superfund site in the Silver Valley.
Nitrate from irrigation and dairies is a concern in the Magic Valley and other agricultural areas, especially for private wells. Naturally occurring arsenic affects some groundwater systems statewide. In the Silver Valley region, legacy mining contamination requires ongoing management.
Idaho private-well owners should test for nitrate, arsenic, and bacteria, particularly in irrigated regions. Reverse osmosis removes nitrate, arsenic, and uranium effectively. Municipal customers generally enjoy good water but should review their Consumer Confidence Report and address any lead plumbing in older homes.
Most Idaho cities we grade have tap water in good standing with EPA. With an average score of 90/100 across 20 graded cities, Idaho generally has good water quality. However, water quality varies by utility, so check your specific city's report.
The most common water quality concerns in Idaho include nitrates (irrigated agriculture), arsenic (naturally occurring in groundwater), heavy metals (northern mining legacy). These contaminants can come from natural sources, industrial activities, or aging infrastructure. Review your city's specific report to see which contaminants affect your area.
Whether you need a water filter depends on your specific location and health concerns. Most Idaho cities have water that meets EPA standards, though some residents prefer additional filtration for taste or extra protection. Look for filters certified by NSF/ANSI to remove the specific contaminants found in your area.
Public water systems in Idaho are required to provide annual Consumer Confidence Reports (CCRs) to residents. You can usually find your report on your water utility's website, request it by phone, or access it through the EPA's database. Our city-level reports above summarize key information from these official sources.
Lead can be present in Idaho water, primarily from older plumbing infrastructure. Homes built before 1986 may have lead pipes or lead solder. While water treatment plants remove lead, it can leach into water from service lines and home plumbing. Check your city's specific report for lead testing data, and consider having your tap water tested if you live in an older home.
PFAS ("forever chemicals") have been detected in water systems across the United States, including in Idaho. These chemicals are associated with industrial sites, military bases, and firefighting foam use. The EPA has set new PFAS limits effective 2024. Check individual Idaho city reports for PFAS testing results in your area.
On EPA records, Caldwell has the highest water quality score in Idaho at 100/100 (Grade A). However, "best" depends on your specific health concerns. View our Best Water Quality in Idaho page for a complete ranking.
Public water systems in Idaho are required by the EPA to test water regularly. Testing frequency depends on the contaminant: bacteria testing occurs daily to weekly, while chemical contaminants may be tested quarterly or annually. Results are published in annual Consumer Confidence Reports. Our site aggregates this data from EPA's SDWIS database.
Compare water quality across counties and find data for your area