Private well owners need to test their drinking water

By Mike Ekberg, manager of water resources monitoring and analysis

Municipal public water systems in Ohio are required to test drinking water for contaminants on a regular basis. For many parameters, that is daily. This helps to ensure the water they produce is safe for consumers to drink.

Private well owners, on the other hand, are not typically required to test their drinking water once their private water system has been installed and has undergone an initial test for total coliform, E. coli, and nitrates. Testing your water more routinely can seem overwhelming, but we can help.

We recommend that well owners test their water at least annually for bacteria, nitrate, and any local contaminants of concern. More frequent testing should be considered if any of the following conditions apply:

  • There is a change in the taste, odor, or appearance of the well water, or if a problem occurs such as a broken well cap, inundation by floodwaters, or a new contamination source
  • The well has a history of bacterial contamination
  • The septic system has recently malfunctioned
  • Family members or house guests have recurrent incidents of gastrointestinal illness
  • An infant is living in the home
  • To monitor the efficiency and performance of home water treatment equipment

Private well owners may also want to consult your local health department for recommendations regarding type and frequency of testing specific to your location.

Another reason to test: Increasing precipitation in our region may increase risk of bacterial contamination

Annual precipitation in the Miami Valley is increasing. The 30 year mean annual precipitation for 1951 – 1980 was about 37 inches. Mean annual precipitation for 1991 – 2020 is about 42 inches. That is an increase of 5 inches. With the increased precipitation comes the increased risk for flooding around your well. Flooding or heavy rainfall can allow bacteria from animal and human feces as well as other contaminants to seep into wells, particularly if the well is not properly constructed or sealed. Recent studies have associated high levels of fecal derived bacteria levels in water with intense precipitation events and flooding of surrounding lands.

Where can I get my drinking water tested?

You have a couple options to explore.

1. Call your county health department. They may provide water testing for bacteria and nitrates. If you want to test for other contaminants, the county health department should be able to provide you with a list of area state-certified drinking water testing labs.

2. View a list of certified laboratories on Ohio EPA’s website.

3. Contact a nearby municipal public water system. Often the regional, city or county public water system laboratories have the capability to run bacteria tests. They may be willing to provide this service to interested well owners.

4. Attend a Test Your Well Event. As a service to private well owners, MCD fosters a confidential screening program called Test Your Well. Scheduled events allow you to bring a sample of your well water to be tested – at no charge – for the presence of nitrates, arsenic, and bacteria. MCD has tested the water from thousands of private well property owners over the years. We partner with local organizations like county soil and water conservation districts and FFA chapters to hold the events. Test Your Well events are scheduled throughout the year.

Test Your Well events are held at different times throughout the year.

What should I test for?

The following list of contaminants is a good starting point for most Miami Valley well owners.

Total Coliform – At a minimum, well owners in the Miami Valley should test their drinking water for total coliform. The presence of coliform bacteria is an indicator of possible contamination from human or animal wastes. There should not be any total coliform in drinking water.

Nitrate – Common sources of nitrate to well water include fertilizers, septic systems, animal manure, and leaking sewer lines. Some nitrate can also be present naturally from natural breakdown of organic matter, soil, and rocks. High levels of nitrate in drinking water present a health concern and can also indicate the presence of other contaminants such as bacteria and pesticides. Nitrate is particularly toxic to infants when drinking water with high levels of nitrate is mixed in formula.

Arsenic – Arsenic is a naturally occurring contaminant in well water. It’s linked to various cancers and other health issues. A study by MCD in 2011 sampled 107 different private wells in the Miami Valley and found that about 20 percent of the wells had arsenic above the drinking water standard (10 micrograms per liter) for public water systems (Miami Conservancy District, 2011).

Manganese – Manganese also occurs naturally in well water. Typically manganese is a nuisance contaminant causing aesthetic issues such as staining of plumbing fixtures and laundry. However, it can be linked to health issues when present at high enough concentrations.

Lead – Lead typically gets into drinking water from corroded pipes and plumbing fixtures. If your home was built prior to 1986, it’s more likely to have lead pipes, fixtures, and solder. Lead in drinking water is associated with a variety of adverse health effects.

How do I interpret the results?

Interpreting laboratory water test results can be confusing. Often the laboratory can provide a helpful explanation as to whether or not the results exceed any drinking water guidelines. Other options for Miami Valley residents to get help interpreting their test results include:

The most important information to obtain from well water testing is to find out if any of the test results indicate a health risk.

More information for well owners

The National Groundwater Association (NGWA) provides an excellent online resource for well owners at The site provides all kinds of information on water well basics, well maintenance, and information on well water quality and quantity. If you are a well owner interested in learning more about your well, this site is a great resource for you.


Miami Conservancy District, 2011 Study of Arsenic levels in private wells in the Great Miami River Watershed: MCD report no. 2011-06.

Phillis M. J., and Flesher J., 2022 Climate-driven flooding poses well water contamination risks: Associate Press, from URL, accessed June 13, 2022.