About Private Well Data
Tracking Private Well Water Quality involves collecting data about the levels of contaminants that are commonly tested for in private drinking water supplies.
This page provides general information about drinking water quality data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.
Information on this page:
What do these data tell us?
- The number of that had a total coliform test conducted and a positive total coliform test result.
- The percent of wells tested for that had a positive total coliform result
- The number of private water wells that had a fecal coliform test conducted and a positive fecal coliform test result.
- The percent of wells tested for that had a positive fecal coliform result
- The number of private water wells that had an test conducted and an arsenic test result that was in exceedance of the Maximum Concentration Level () for arsenic of 10 micrograms per liter (µg/L)
- The percent of wells tested for arsenic that had a result that was in exceedance of the Maximum Concentration Level (MCL) for arsenic of 10 µg/L
- The number of private water wells that had a nitrate test conducted and a nitrate test result that was in exceedance of the Maximum Concentration Level (MCL) for nitrate of 10 mg/L
- The number of private water wells that had Percent of wells tested for nitrate that had a result that was in exceedance of the Maximum Concentration Level (MCL) for nitrate of 10 mg/L
- The percent of wells tested for nitrate that had a result that was in exceedance of the Maximum Concentration Level (MCL) for nitrate of 10 mg/L
- The number of existing wells that were closed or that were renovated.
Back to top
How can we use these data?
- The data provides summary information on , , and in private wells in Iowa.
- State and local partners can use the data for program planning and evaluation.
Back to top
What can these data not tell us?
- The sources of exposure for contaminants in drinking water.
- Information about water quality in water sources other than private wells.
- The presence of coliform bacteria and nitrates or levels of arsenic in private wells that have not been tested.
Back to top
What are the sources of the data?
- Water samples are collected from private water wells in Iowa and the test results are submitted to the Iowa Department of Natural Resources Private Well Tracking System (PWTS).
- Much of the data in the PWTS is collected as part of the Grants to Counties program through providing funds to local county health departments to provide financial assistance to their residents for private water well services.
Back to top
What time period of data is available?
- The Iowa Public Health Tracking portal displays private water well test data from the year 2000 through the most recent year of data available.
Back to top
Why are the data limited to arsenic, coliform bacteria, and nitrate?
- The Iowa Public Health Tracking portal displays private water well test data of several contaminants that are commonly tested for in private well water through the Grants to Counties program.
- It is recommended that private water wells be tested for nitrate and coliform bacteria each year. These tests are indicators of other potential water quality or well problems.
- Previous studies have found arsenic in multiple groundwater sources around Iowa, since 2015 the Grants to Counties program has supported arsenic testing to better characterize the extent of arsenic in Iowa’s groundwater.
Back to top
What are the limitations of the data?
- These data are limited to private well owners that test their wells.
- Reported concentrations in private wells cannot be directly linked to exposures and health risks, because they do not account for water use and consumption practices. In addition, people may obtain drinking water from other sources (e.g., bottled water, workplace, school).
- Each well is represented by only a single sample, so the data cannot be used to assess well-specific trends in water quality over time.
Back to top
Where can I find more technical information about the data?
More detailed documentation of the private well water data can be found in the following documents:
Descriptive Metadata
Private Well Water Data 
Contact Us to learn more about private well water data, or any of the measures displayed on the Iowa Public Health Tracking Portal.
Back to top