Frequently Asked Questions

See the quality of the water sources near you — it’s easy:


No map marker is shown for a known source of water

Markers on a map at this web site, such as the local water-quality map, indicate locations where water has been tested or observed and recorded in some formal way. They do not indicate all known sources of water, only water for which records are available. It’s also quite possible that data for that water is recorded in some place we have not yet included in our “water explorer” tools… yet! [Editor’s note: we wish the community and household wells of our childhood were included!]

“No results recorded” on reports

When we find a record stating a test was performed, we include that fact in our reports. But sometimes there is no data to display for the test. This might occur for a number of reasons. For example, the test wasn’t really performed, the results were inconclusive or unreliable, someone simply neglected to record the results, etc.

I see a web page saying just “502 Bad Gateway”

That seems to happen sometimes when using the site’s map to show local water-quality reports. The remote server might be overloaded (or just very slow). When we’ve run into that message and try again a few hours later, or the next day, the problem seems to go away and the expected web page loads normally.

Why are you doing this project?

We want to make it easier for more people to learn about the water in their communities, whether they’re urban, suburban, or rural. A recent study concludes that 77% of Americans who are not on well water do not know the source of their supply. We aim to provide easy ways to get such information, and more. Of course, if our work also helps agencies and leaders to better understand and manage these shared resources, we are even happier.

Can I trust the information on this web site?

We get water-quality data from trusted sources and we identify those sources in our reports. We are trying to make it easy to see the source of the data and judge its reliability for yourself.

How accurate are the water-quality tests?

The reports we display may include data from multiple sources, which we identify. While we have no direct knowledge of those sources, it’s informative to see how the U.S. EPA certifies water-testing laboratories.

By necessity, we rely upon the responsible organizations, scientists, technicians and others who are working in the field and in many facilities throughout the country. If you find a case where the source of the info is not clear, or where a source appears to be providing unreliable data, please contact us with specifics and instructions for how we can repeat your results (so we can know when we’ve fixed something).

How current is the water data shown in the site’s water maps and water-quality reports?

Where we know it, the date of a test should be shown in our reports. We cannot vouch for how recent the data is for any particular location, but we can share the following about the practices of a couple of major data providers:

USGS NWIS — Water-resources data collected from approximately 1.5 million sites in all U.S.A. states, the District of Columbia, Puerto Rico, the Virgin Islands, Guam, American Samoa, and the Commonwealth of the Northern Mariana Islands. NWIS is updated every 24 hours. Data recently added to NWIS may not be immediately accessible. Data is available for each location since the beginning of the database.

USEPA STORET — A data warehouse for water quality, biological, and physical data used by state environmental agencies, EPA, other federal agencies, universities, private citizens, and others. STORET is updated weekly on Thursday evening. Data recently added to STORET may not be immediately accessible through the WQP. The portal will return data from each location since the beginning of the database.

Should I be alarmed if certain substances/characteristics show up in my water-supply report?

Their presence in a water sample might not necessarily indicate danger; that can only be known by referring to authoritative references and public-health medical authorities. And it’s not only “what is there,” but also “how much of it is there?” This site does not make determinations as to threat, risk, healthfulness, danger, etc. We may provide access to third-party sources of such information and, in some cases, we may summarize such information on this site with appropriate credit. But we are not medical or public health experts!

The U.S.A. EPA Substance Registry Services (SRS) is the Environmental Protection Agency’s (EPA) central system for information about substances that are tracked or regulated by EPA or other sources. The agency intends for it to be the authoritative resource for basic information about chemicals, biological organisms, and other substances of interest to EPA and its state and tribal partners.

The system provides a common basis for identification of, and information about:

  • Chemicals
  • Biological organisms
  • Physical properties
  • Miscellaneous objects