Before we ever show up at someone's door, we often tell them to do one thing: go to the EWG Tap Water Database, type in their zip code, and take a look at what comes back.
Most people have never heard of it. Some find it, look at the numbers, and feel a little unsettled. A few call back the same day.
That reaction makes sense. The Environmental Working Group's Tap Water Database is one of the most useful free tools available to any homeowner in this country, and almost nobody knows it exists. It pulls testing data from nearly 50,000 water utilities across the United States and lets you see, in plain terms, what has been detected in your local water supply — and how those levels compare not just to what's legal, but to what scientists consider genuinely protective of long-term health.
Those two things are not the same.
What the Database Actually Shows You
When you search your zip code, you'll get a report for your local water utility. That report lists every contaminant detected in water tests submitted to state environmental agencies, covers data going back several years, and tells you two numbers for each contaminant: the legal limit set by the EPA and the health guideline set by EWG.
The legal limit is the line a utility cannot cross without violating federal law. The EWG health guideline is a separate number, often much stricter, based on current peer-reviewed science about long-term exposure and cancer risk, developmental effects, or other health impacts.
Here's the thing: a utility can be in full legal compliance and still have multiple contaminants that exceed EWG's health guidelines. That's not a technicality. It reflects the fact that, as EWG notes on their site, legal limits for many contaminants in tap water have not been meaningfully updated in nearly 20 years.
A Real Example: Johnson City, Tennessee
The Johnson City Water Department serves more than 100,000 people in and around the city from surface water sources. According to the EWG Tap Water Database, testing from 2014 through 2024 found 18 contaminants in the water — 9 of which exceed EWG's health guidelines.
Two of those are worth looking at directly.
Bromodichloromethane, a disinfection byproduct formed when chlorine interacts with organic matter in source water, was detected at 3.81 parts per billion. EWG's health guideline for this contaminant is 0.06 ppb. That's 64 times above the guideline. There is no federal legal limit for bromodichloromethane — meaning the utility is not violating any law. The water is legal. But 64 times above the health guideline is not a number that gives most parents a lot of comfort.
Chloroform, another disinfection byproduct in the same family, was detected at 20.9 ppb. EWG's health guideline is 0.4 ppb. That's 52 times over.
Again: legal. In compliance. No violation.
This is precisely the gap between "legal" and "safe" that the EWG database makes visible. Johnson City's water is treated, regulated, and meets all federal standards. It is also delivering disinfection byproducts to more than 100,000 people at levels that exceed health-based guidelines by a wide margin. Both of those things are true at the same time.
The database doesn't tell you what to do about it. That's not its job. Its job is to show you what's there.
How to Look Up Your Own Water
The lookup takes about two minutes.
Go to ewg.org/tapwater. You'll see a search field on the main page. Type in your zip code and hit enter. If multiple utilities serve your area, your water bill will have your utility name on it — use that to select the right one.
What you'll see:
Total contaminants detected. The full list of everything found in testing, going back several years.
Contaminants exceeding guidelines. The ones highlighted at the top. These are the EWG health guidelines, not legal limits — read them as a health-protective standard, not a compliance standard.
Each contaminant's story. Click any contaminant and you get the detected level, the national average, the state average, the EWG health guideline, what health effects the research links to it, and what type of filter removes it.
Filter recommendations. At the bottom of each utility page, EWG shows which filter types address the contaminants in that specific water supply.
A few things worth knowing as you read:
The data is from utility-submitted testing, which is required by law. Utilities test regularly and report to state agencies; EWG collects and standardizes that data. This is not EWG's own testing — it is the utility's own numbers, presented with an added analysis layer that the utility's annual water quality report typically doesn't provide.
The EWG health guidelines are often based on California's Office of Environmental Health Hazard Assessment standards, which are among the most protective in the country. Some people find them strict; the underlying science behind them is peer-reviewed.
What the Database Does Not Tell You
This is important. The EWG Tap Water Database covers municipal water supplies. If your home is on a private well, your water is not in the database, because private wells are not regulated and not tested by any utility. There is no reporting requirement. What comes out of your well is entirely your responsibility to know.
If you are on a well, the database is a starting point for understanding what contaminants are common in your region — but it cannot tell you what is actually in your specific water. That requires testing.
The database also shows utility-level averages, not home-level measurements. Even within the same utility service area, water can vary based on how far you are from the treatment plant, the age of the pipes in your neighborhood, and conditions in your home's plumbing. Two homes on the same street can have meaningfully different water.
What to Do With the Information
Dan's recommendation, after people look at their EWG results, is consistent: don't panic, and don't skip straight to buying a filter based on what you see there. Use it as a starting point.
The EWG database shows what the utility is delivering. A free in-home water test shows what's actually coming out of your tap, which can differ from the utility average based on pipe age, household plumbing, and local conditions. The test is free, takes about 20 minutes at your kitchen counter, and gives you a specific picture of your home's water rather than a regional average.
From there, you can make an informed decision about whether treatment makes sense, what kind, and what the cost-benefit looks like for your family. No pressure to buy anything. That's not how the process works.
If you're in the Tri-Cities area or the surrounding region, you can request a free water test at mvpwater.net or call 423-218-9361.
If you're not in the area, the EWG database is still the right first step. Use it to understand what your utility is delivering, then find a certified local provider who will test your home's specific water before recommending anything.
