The Power of Information

National Drinking Water Database


National Drinking Water Database - FAQ

Frequently Asked Questions (FAQs)


1. Where did the data in your database come from?

EWG requested water contaminant data from public and environmental health agencies from around the country. We then painstakingly compiled nearly 20 million records we received from 45 states to create the National Tap Water Quality Database. EWG released the first version of the database in 2005, and updated it in 2009.

2. Does the EPA have a similar database available on-line somewhere?

No. But they should. In fact, the 1996 Safe Drinking Water Act Amendments require the Environmental Protection Agency (EPA) to produce just such a public service. Almost 15 years later, it still hasn't. EWG's Tap Water Database will continue to fill in this important gap in the meantime, but we hope that the EPA will soon live up to its mandate.

3. How does your data differ from the annual water quality report I receive from my water utility?

Federal law requires water utilities to provide their customers with an annual report on contaminants in their drinking water. These reports, however, provide only a partial picture of what people are actually drinking.

  • They contain only average levels (and the range detected) for most contaminants, as opposed to a full reporting of all test results.
  • They are not required to include the many unregulated chemicals utilities are choosing to test for, above and beyond state and federal monitoring requirements. EPA requires reported only for regulated chemicals and for those unregulated chemicals included in special, mandatory testing programs.
  • Utilities are not required to report on chemicals that are found above health guidelines. They must list violations of legal limits in their annual reports, but these limits are often much higher than government health guidelines, since legal limits are adjusted upward to help reduce treatment costs.

4. Your database does not have any information about my water system. Where can I find this information?

Although the database is very extensive, EWG was unfortunately not able to obtain data for every water utility in every state. If you are interested in water quality information for a system that is not in the database, you should contact that water utility directly. In virtually all cases, community water systems in the U.S. are required to produce an annual "Consumer Confidence Report" (CCR) that contain information on contaminants found in local drinking water, and the water system's compliance with drinking water standards and rules. The largest utilities are required to post their CCR's on-line; other systems will provide you a copy upon request.

5. Is my tap water safe to drink?

The United States enjoys one of the cleanest and safest supplies of drinking water in the world. Municipal utilities provide water that comply with existing state and federal standards in more than 92% of cases. At the same time, we also know that there are many unregulated contaminants in our nation's drinking water. If you are concerned about the safety of your drinking water, EWG suggests that you purhcase a home water filter. EWG has developed an extensive on-line guide to choosing a water filter to help you determine which one is right for you.

7. Is bottled water safer than tap water?

Bottled water is not necessarily any safer than tap water. In fact, some reports show that up to 44 per cent of bottled water is just tap water filtered in some cases and untreated in others. The problem with bottled water is that you are never sure exactly what you are getting. Where as tap water suppliers are required to disclose the level of any contaminant found in their supply, bottled water manufacturers have no such requirements. A previous EWG report found that 4 out of every 5 bottled waters analyzed did not publish results of water quality testing. In addition to the typical drinking water contaminants, bottled waters may also be contaminated with plastic additives. Many of these additives have not been fully assessed for safety and have been shown to migrate from the bottles into bottled water to be consumed. See EWG's Bottled Water Quality Investigation and Bottled Water Label Scorecard for more information.

8. I'm really concerned about the contaminants in my tap water. What should I do?

EWG suggests purchasing a home water filter. EWG has developed an extensive on-line guide to water filters to help you determine which one is right for you. If you are getting your water from a private well, EWG also recommends getting your water tested regularly.

9. Where can I get my water tested?

There are numerous labs around the country that do water testing for common contaminants. There are also home test kits available on-line. EWG does not make any specific recommendations for labs to use or kits to purchase. We do, however, strongly recommend that people using private wells test their water regularly. The New Jersey Department of Health has an excellent 27 page guide to private well testing that we suggest reading.

10. What kind of water filter should I buy?

It depends what you are looking for. EWG has developed an extensive on-line guide to choosing a water filter to help you answer this question.

11. Where does my tap water come from?

Drinking water sources vary greatly across the country, and even within communities. According to the Environmental Protection Agency, 30 percent of community water systems nationwide relied on surface water taken from rivers, lakes, and reservoirs, and 70 percent relied on groundwater pumped from wells (EPA 2009u). For more information on where your tap water is coming from contact your local water utility.

12. Are some people more sensitive to water contaminants than others?

Yes. The Environmental Protection Agency notes that people with severely compromised immune systems, such as people with cancer undergoing chemotherapy, people who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. The EPA suggests that these people seek advice about drinking water from their health care providers.

13. My tap water has a funny smell/taste/color. Should I be concerned?

Unpleasant smells, colors, or tastes do not necessarily mean that your water is unsafe to drink. However, these can be important indicators of potential safety problems. EWG recommends that you contact your local water supplier to investigate the problem. If the unpleasant smell, color, or taste is related to something benign, a home water filter can help solve the issue. EWG has developed an extensive on-line guide to choosing a water filter to help you choose a filter that might help solve your problem.

14. My water smells like chlorine. What do I do?

Each individual water system regulates its own use of chlorine to disinfect water. Especially after large rainstorms, your water system may add more chlorine so as to treat potentially larger numbers of microorganisms that end up in water due to animal farm runoff or storm sewer discharges. To deal with chlorine and chlorination byproducts, you may consider installing a home water filter specifically designed to remove chlorine from the drinking water. EWG has developed an extensive on-line guide to choosing a water filter to help you find the right one for you.

15. My community has issued a boil water alert. What does that mean? How long will it last?

Under the provisions of the Safe Drinking Water Act, water systems that serve more than 25 people are required to test their water regularly for a wide variety of contaminants. If a water system has issued a boil water alert, it has likely discovered one or more microbiological contaminants at levels exceeding those allowed by the EPA. The water system must then take appropriate corrective action, continue to monitor its water supply, and notify customers when it has remedied the problem.