How to Read Your EWG Tap Water Report (And What to Do Next)

What Is the EWG Tap Water Database?

If you have ever searched for information about your local drinking water quality, you have probably come across the Environmental Working Group's Tap Water Database. It is the largest publicly accessible resource for U.S. drinking water quality data in existence, covering nearly 50,000 community water systems and drawing on approximately 31 million test results for 534 chemicals collected between 2021 and 2023.

The database is built on data that water utilities are legally required to collect and report to the EPA under the Safe Drinking Water Act of 1974. EWG takes that raw government data and makes it searchable, visual, and — most importantly — compares it against health-based standards that are often far more protective than the federal legal limits your utility is required to meet.

Understanding how to read your report is the difference between knowing your water is "legal" and knowing whether it is actually safe.

How to Pull Up Your Report

Getting your report takes about 30 seconds:

1. Go to ewg.org/tapwater

2. Enter your ZIP code in the search bar

3. Select your water utility from the list (most ZIP codes have one, but some have several)

4. Your full water quality report loads immediately

The report shows every contaminant detected in your water, the level at which it was found, and how that level compares to both the federal legal limit and EWG's own health guideline.

The Two Numbers That Matter Most

Every contaminant in your EWG report is shown with two comparison points, and understanding the difference between them is the key to reading the report correctly.

The federal legal limit (MCL) is the Maximum Contaminant Level set by the EPA — the concentration at which your utility is required to take action. These limits are set through a regulatory process that balances health risk against the cost of treatment. Many of them have not been updated in decades. A contaminant being "below the legal limit" does not mean it poses no health risk. It means your utility is in compliance with a standard that may be outdated.

EWG's health guideline is a separate number, calculated by EWG scientists based on the most current peer-reviewed research on health effects. These guidelines are typically set at the level where the risk of cancer or other harm over a lifetime of exposure is considered negligible — often one additional cancer case per million people. EWG's guidelines are almost always stricter than federal limits, sometimes by orders of magnitude.

When you see a contaminant listed as exceeding the EWG health guideline but not the legal limit, that means your water is technically legal but may still pose a long-term health risk based on current science.

What the Contaminant List Tells You

Your report will list contaminants in two categories:

Regulated contaminants are chemicals for which the EPA has set a legal limit. If any of these appear in your report above the legal limit, your utility is in violation and is required to notify you. Most utilities are in compliance with regulated contaminants — but compliance does not mean safe.

Unregulated contaminants are chemicals that the EPA monitors through its Unregulated Contaminant Monitoring Rule (UCMR) program but has not yet set a legal limit for. This category includes many PFAS compounds, some disinfection byproducts, and emerging contaminants that science has identified as harmful but regulation has not yet caught up to. Finding an unregulated contaminant in your water does not mean your utility did anything wrong — it means the regulatory system has not addressed it yet.

The most commonly detected contaminants across U.S. water systems include:

Why Your Water Can "Pass" and Still Contain Harmful Chemicals

This is the part of the EWG report that surprises most people. Your utility can send you a Consumer Confidence Report every year showing full compliance with all federal standards — and your EWG report can simultaneously show multiple contaminants exceeding health-based guidelines.

Both things can be true at the same time. Here is why.

The EPA's legal limits were largely established in the 1970s and 1980s, based on the science available at the time and the cost of treatment. Since then, research has identified health effects at much lower concentrations than the original limits assumed. Updating those limits requires a lengthy regulatory process that often takes decades. In the meantime, utilities are only required to meet the old standards.

EWG's health guidelines reflect the current science. When you see a contaminant flagged in your EWG report despite your utility being in compliance, it is a signal that the regulatory system has not caught up to what researchers now know about that chemical.

How to Use Your Report to Make Decisions

Once you have read your EWG report, here is how to turn that information into action:

Step 1: Identify your highest-concern contaminants. Look for anything that exceeds EWG's health guideline, not just the legal limit. Pay particular attention to carcinogens (arsenic, chromium-6, PFAS, disinfection byproducts) and contaminants with neurological effects (lead, nitrate for infants).

Step 2: Cross-reference with your Consumer Confidence Report. Your utility is required to mail you an annual water quality report. This report gives you the actual measured concentration of each contaminant, which helps you understand the magnitude of any exceedance.

Step 3: Match your filtration to your specific contaminants. Not all filters remove all contaminants. A standard pitcher filter with activated carbon is effective against chlorine, some disinfection byproducts, and certain heavy metals — but it does not remove nitrate, arsenic, or PFAS at meaningful levels. Reverse osmosis systems are the most broadly effective option for a wide range of contaminants. Whole-house systems treat all water entering your home, including shower and bath water, which matters for contaminants like chloroform that are absorbed through skin and inhaled as steam.

Step 4: Consider getting your water independently tested. If your EWG report shows concerning levels of specific contaminants, or if you have a private well that is not covered by the EWG database, an independent lab test gives you precise, current measurements for your specific tap.

The Bottom Line

The EWG Tap Water Database is one of the most powerful free tools available for understanding what is in your drinking water. The key is knowing how to read it: focus on EWG's health guidelines, not just the federal legal limits, and pay attention to both regulated and unregulated contaminants.

Your water being "legal" is a starting point, not an endpoint. The EWG report gives you the information you need to go further — to understand what your utility's compliance report does not tell you, and to make informed decisions about protecting your family's health.

If you want to know exactly what is in your local water supply, get your free personalized water report from FranklyH2O. We pull the latest EPA data for your ZIP code and translate it into plain language — no chemistry degree required.

Sources: Environmental Working Group (EWG), U.S. Environmental Protection Agency (EPA), Centers for Disease Control and Prevention (CDC), Safe Drinking Water Act (1974).