Last updated: February 2026
What Is the EWG Tap Water Database?
The Environmental Working Group (EWG) Tap Water Database is a free online tool that compiles water quality testing data from nearly 50,000 water utilities across the United States. It covers water systems serving approximately 280 million Americans.
What makes it valuable: while your water utility's annual Consumer Confidence Report tells you whether contaminants are within legal limits, the EWG database goes further — comparing detected levels against health-based guidelines derived from the latest peer-reviewed research.
This distinction matters. EPA legal limits (Maximum Contaminant Levels) often allow concentrations hundreds or thousands of times higher than what scientists consider safe. EWG's guidelines fill that gap.
💡 Quick fact: EWG's analysis found that virtually every U.S. water system tested contained at least one contaminant above health guidelines — even when in full legal compliance with EPA standards.
How to Use the EWG Database (Step by Step)
Checking your water takes about 60 seconds:
Step 1: Visit the Database
Go to ewg.org/tapwater in your browser. You'll see a search bar prominently displayed on the page.
Step 2: Enter Your Zip Code
Type your 5-digit zip code and click search. If multiple utilities serve your area, you'll see a list — select the one that matches your water bill.
Step 3: Review Your Utility Report
Your report will show:
- Number of contaminants detected (total found in testing)
- Contaminants above health guidelines (exceeding EWG's science-based limits)
- Contaminants above legal limits (exceeding EPA's MCLs — rare but serious)
Step 4: Click Individual Contaminants
Click on any contaminant to see:
- The amount detected in your water
- The EWG health guideline
- The EPA legal limit
- Health effects and research citations
- How your utility compares to the national average
Understanding Your Results
EWG color-codes results to make them easier to understand:
Green — Low Concern
Contaminant detected but below EWG's health-based guideline. Still worth monitoring, but not an immediate concern.
Yellow/Orange — Moderate Concern
Exceeds EWG's health guideline but still within EPA legal limits. This is the most common finding. Consider filtration.
Red — High Concern
Exceeds EPA legal limits. This means your utility is in violation. Use filtration immediately and consider reporting to your state health department.
What "X Contaminants Detected" Means
Don't panic at a high number. Detecting a contaminant doesn't mean it's at dangerous levels. What matters is:
- How many exceed health guidelines (EWG's science-based levels)
- How many exceed legal limits (EPA's enforceable standards)
- By how much they exceed — 2x over a guideline is very different from 200x
EPA Legal Limits vs. EWG Health Guidelines
This is the most important concept to understand. Here's why the numbers differ so dramatically:
| Contaminant | EWG Health Guideline | EPA Legal Limit | Difference |
|---|---|---|---|
| Haloacetic Acids (HAA5) | 0.1 ppb | 60 ppb | 600x |
| Trihalomethanes (THMs) | 0.8 ppb | 80 ppb | 100x |
| Chromium-6 | 0.02 ppb | No federal limit | ∞ |
| Arsenic | 0.004 ppb | 10 ppb | 2,500x |
| PFOA | 0.1 ppt | 4 ppt | 40x |
| Nitrate | 0.14 mg/L | 10 mg/L | 71x |
Why such a big gap? EPA legal limits consider what's technically and economically feasible for utilities. EWG health guidelines consider only health research. Neither is "wrong" — but if your goal is to minimize health risk, EWG's guidelines are the better benchmark.
Most Common Contaminants Found Nationwide
Based on EWG's nationwide analysis, these contaminants show up most frequently above health guidelines:
- Haloacetic Acids (HAA5/HAA9) — Found in virtually every chlorinated system. Byproducts of the disinfection process. Linked to cancer and reproductive issues.
- Trihalomethanes (THMs) — Another disinfection byproduct class. Present wherever chlorine is used. Associated with bladder cancer.
- Chromium-6 — The "Erin Brockovich chemical." Found in water serving 200+ million Americans. No federal limit exists.
- Nitrate — From agricultural runoff. Most common in rural and farming areas. Dangerous for infants.
- Radiological contaminants — Radium, uranium, and combined radium. Naturally occurring but elevated in some regions.
- PFAS — Increasingly detected as testing improves. Read our full PFAS guide →
- Arsenic — Naturally occurring in groundwater, especially in the western U.S.
Limitations of the EWG Database
While the EWG database is an excellent starting point, it has important limitations:
- Utility-level data, not tap-level: Results show what was found at the treatment plant or distribution system — not at your specific faucet. Lead, for example, enters water from your home's plumbing, not the utility's source.
- Historical data: Results typically reflect testing from the most recent compliance period (3-5 years). Current conditions may differ.
- No well water coverage: Only public water systems are included. Private well users need independent testing. See our well water guide →
- Not all contaminants tested: Utilities only test for EPA-regulated contaminants. Emerging contaminants like microplastics, pharmaceuticals, and some PFAS compounds may not appear.
- Seasonal variation: Water quality can change seasonally. Annual averages may mask spikes during certain periods.
Our recommendation: Use the EWG database as your starting point, then follow up with a home water test kit for the most accurate picture of what's in your specific tap water.
What to Do If Your Water Has Issues
If Contaminants Exceed Health Guidelines (But Not Legal Limits)
This is the most common scenario. Your water is "legal" but contains contaminants at levels health research suggests aren't ideal for long-term exposure. Steps to take:
- Identify your top contaminants — Note which specific substances are elevated
- Test your tap — A home test kit confirms whether utility-level data matches your specific faucet
- Choose the right filter — Different contaminants require different filtration technologies (see below)
If Contaminants Exceed Legal Limits
This is more serious. Your utility should be notifying you and taking corrective action. In the meantime:
- Install filtration immediately — An RO system provides the broadest protection
- Contact your utility — Ask what corrective actions they're taking
- Report to your state — Contact your state's drinking water program
- Consider using bottled water for drinking and cooking until the issue is resolved
Recommended Filters Based on Your Results
Match your filter to your contaminants:
| If You Found... | Best Filter Type | Our Pick |
|---|---|---|
| PFAS / Forever chemicals | Reverse Osmosis or Activated Carbon (NSF P473) | APEC ROES-50 |
| Lead | Reverse Osmosis or NSF 53 certified pitcher | iSpring RCC7AK |
| Disinfection byproducts (HAAs/THMs) | Reverse Osmosis or Activated Carbon | Waterdrop G3P800 |
| Arsenic | Reverse Osmosis | APEC ROES-50 |
| Nitrate | Reverse Osmosis or Ion Exchange | iSpring RCC7AK |
| Chlorine taste/smell only | Basic Carbon Pitcher | Brita Standard Pitcher |
| Multiple contaminants | Reverse Osmosis (broadest coverage) | Waterdrop G3P800 |
APEC ROES-50
~$200
5-stage RO system. Removes 99%+ of all major contaminants. Made in USA. The most reliable budget RO system available.
View on Amazon →iSpring RCC7AK
~$250
6-stage with alkaline remineralization. Better tasting water than standard RO. NSF/ANSI 58 certified. Excellent for families.
View on Amazon →Waterdrop G3P800
~$700
Tankless, 800 GPD, smart TDS monitor. No waiting for tank to fill. The best overall RO system on the market.
View on Amazon →Want More Accurate Data Than EWG?
A home water test kit reveals exactly what's in your specific tap — including lead from your pipes that utility-level data won't show.
Browse Water Test Kits on Amazon →Frequently Asked Questions
What is the EWG Tap Water Database?
The EWG Tap Water Database is a free online tool from the Environmental Working Group that lets you look up water quality data for your local utility by zip code. It compares detected contaminants against both EPA legal limits and EWG's stricter health-based guidelines, covering nearly 50,000 utilities serving 280+ million Americans.
Is the EWG Tap Water Database accurate?
The database uses official data reported by water utilities to the EPA and state agencies. The contaminant data is accurate, but it reflects utility-level testing — not what comes out of your specific faucet. For the most accurate personal results, supplement EWG data with a home water test kit.
How often is the EWG database updated?
EWG updates the database periodically as new utility compliance data becomes available from the EPA. Most data reflects the most recent 3-5 year testing period. Check the "data available" date on your utility's report for specifics.
Why does EWG say my water has contaminants above guidelines when my utility says it's safe?
EWG uses health-based guidelines that are typically much stricter than EPA legal limits. Your water can be 100% legally compliant while exceeding health guidelines because EPA limits factor in cost and feasibility, not just health. EWG guidelines are based purely on the latest health research.
Does the EWG database cover well water?
No. The EWG database only covers public water systems. If you use a private well, you'll need to test independently. Read our well water guide for testing recommendations.