Last updated: February 2026
How We Ranked the States
Our rankings are based on a composite analysis of multiple data sources:
- EPA Safe Drinking Water Act violations — Number and severity of violations per capita
- EWG contaminant data — Average number of contaminants above health guidelines
- PFAS contamination — Known PFAS sites and detection levels
- Infrastructure age — Lead service line estimates and infrastructure investment
- State regulations — Whether the state sets standards stricter than federal minimums
- Source water quality — Natural vulnerability of water sources to contamination
💡 Important caveat: State rankings provide a general picture, but water quality varies enormously within each state. A town in a "worst" state may have excellent water, while a town in a "best" state may have problems. Always check your specific utility's data.
Top 10 States for Tap Water Quality
Oregon
Portland's Bull Run Watershed is one of America's most pristine water sources. Low industrial contamination, strong state regulations, and excellent infrastructure investment.
Colorado
Mountain snowmelt provides exceptionally clean source water. Denver Water has invested heavily in infrastructure. Few EPA violations statewide.
Vermont
Low population density, minimal industrial contamination, and strict environmental regulations. Small water systems with excellent source protection.
New Hampshire
Clean mountain and lake sources. State has set PFAS limits stricter than federal standards. Proactive monitoring and treatment programs.
Hawaii
Volcanic aquifers provide naturally filtered water. Low agricultural contamination compared to mainland states. Limited industrial sources.
Minnesota
10,000+ lakes provide abundant clean source water. Strong state environmental agency. Proactive approach to PFAS from 3M contamination in Twin Cities.
Massachusetts
Quabbin Reservoir system is world-class. State has aggressive PFAS standards. Major infrastructure investment in greater Boston system.
Connecticut
Well-protected watershed sources. State PFAS standards among strictest nationally. Modern treatment infrastructure in most systems.
Rhode Island
Scituate Reservoir provides clean source water. Small state with manageable oversight. Recent infrastructure investments.
Washington
Cascade mountain sources with naturally clean water. Seattle's Cedar River Watershed is protected old-growth forest. Strong state regulations.
10 States with the Worst Tap Water
Texas
Leads the nation in EPA violations. Massive agricultural runoff, aging infrastructure, and limited state regulation. Many small rural systems chronically out of compliance.
Florida
Widespread PFAS contamination from military bases. Naturally occurring radium in groundwater. Agricultural runoff and algae blooms impact surface water sources.
Arizona
Naturally occurring arsenic in groundwater. Colorado River source water quality declining. PFAS contamination near military installations including Luke AFB.
Oklahoma
High rates of EPA violations. Oil and gas industry impacts groundwater. Many rural systems lack resources for proper treatment and infrastructure.
New Mexico
Arsenic and uranium naturally present in groundwater. PFAS from Holloman and Cannon Air Force Bases. Limited water resources exacerbate quality issues.
Louisiana
"Cancer Alley" industrial corridor along Mississippi River. Heavy industrial discharge. Many small systems with chronic violations.
Georgia
Aging infrastructure, particularly in Atlanta metro. Agricultural runoff. PFAS contamination near military bases.
Ohio
Lake Erie algae blooms (Toledo crisis of 2014). Lead service lines throughout older cities. Industrial legacy contamination.
Pennsylvania
Severe PFAS contamination in eastern PA (Bucks/Montgomery counties). Coal mining legacy. Lead pipes in Philadelphia and Pittsburgh.
California
Varies wildly by region. Central Valley has severe nitrate and 1,2,3-TCP contamination. PFAS near military bases. Chromium-6 widespread. Some cities like San Francisco have excellent water.
Full State Rankings Overview
| Rank | State | Grade | Key Issues |
|---|---|---|---|
| 1 | Oregon | A | Pristine sources, strong regulations |
| 2 | Colorado | A | Mountain snowmelt, good infrastructure |
| 3 | Vermont | A | Low contamination, strict environmental laws |
| 4 | New Hampshire | A | Clean sources, proactive PFAS standards |
| 5 | Hawaii | A | Volcanic aquifer filtration |
| 6 | Minnesota | A- | Abundant lakes, PFAS cleanup underway |
| 7 | Massachusetts | A- | Quabbin Reservoir, strict PFAS rules |
| 8 | Connecticut | B+ | Protected watersheds, modern treatment |
| 9 | Rhode Island | B+ | Clean reservoir, infrastructure investment |
| 10 | Washington | B+ | Mountain sources, strong oversight |
| 11-20 | Montana, Maine, Idaho, South Dakota, North Dakota, Wyoming, Wisconsin, Utah, Alaska, Iowa | ||
| 21-30 | Missouri, Kentucky, New York, Virginia, Maryland, Michigan, Nebraska, Kansas, Tennessee, Indiana | ||
| 31-40 | Nevada, North Carolina, South Carolina, West Virginia, Illinois, Alabama, Mississippi, Arkansas, New Jersey, Delaware | ||
| 41-50 | California, Pennsylvania, Ohio, Georgia, Louisiana, New Mexico, Oklahoma, Arizona, Florida, Texas | ||
What Determines Water Quality?
Source Water
Where water comes from matters enormously. Mountain snowmelt and protected watersheds (like Oregon's Bull Run or Massachusetts' Quabbin) start with minimal contamination. Groundwater in agricultural areas often contains nitrates and pesticides. River water downstream from cities picks up everything upstream communities discharge.
Infrastructure Age
The American Society of Civil Engineers gives U.S. drinking water infrastructure a grade of C-. Many systems rely on pipes installed 50-100+ years ago. An estimated 6 billion gallons of treated water are lost daily to leaks — and those same cracks let contaminants in.
State Regulations
States can set standards stricter than the EPA's federal minimums. States like New Hampshire, Massachusetts, and New Jersey have set their own PFAS limits. Others default to federal minimums or have weaker enforcement. Some states have explicitly blocked local communities from setting stricter standards than state law.
Funding and Investment
The EPA estimates $625 billion in infrastructure investment is needed over the next 20 years. Wealthier states and cities can invest more. Small rural systems — particularly in states like Texas, Oklahoma, and Louisiana — often lack resources for proper treatment.
How to Protect Yourself Regardless of State
Even in top-ranked states, no tap water is completely free of contaminants. Here's what to do:
- Check your specific water: Use the EWG database — your town may differ from the state average
- Test your tap: A home test kit reveals what's in your specific water
- Filter your water: An RO system provides comprehensive protection in any state
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Which state has the best tap water?
Oregon consistently ranks #1 thanks to Portland's pristine Bull Run Watershed, low industrial contamination, and strong state regulations. Colorado, Vermont, New Hampshire, and Hawaii round out the top 5.
Which state has the worst tap water?
Texas ranks last due to the highest number of EPA Safe Drinking Water Act violations, aging infrastructure, agricultural runoff, and limited state regulation — particularly for small rural systems. Florida and Arizona also rank near the bottom.
Is tap water quality the same across an entire state?
No. Quality varies dramatically by city, county, and even neighborhood. California, for example, ranges from excellent (San Francisco) to severely contaminated (Central Valley farming communities). Always check your specific utility.
What factors determine tap water quality?
Source water quality (surface vs groundwater), infrastructure age and condition, treatment methods, proximity to contamination sources (industry, military bases, farms), state regulatory standards, and natural geology (arsenic, radium in some regions).
Does a high state ranking mean I don't need a filter?
Not necessarily. Even top-ranked states have contaminants above health guidelines in most systems. If you want the cleanest possible drinking water, a filter helps regardless of where you live. The good news: in top-ranked states, even a basic carbon filter may be sufficient.