Private Well Testing
Testing drinking water at the State Hygienic Lab

The purpose of this web page is to inform private well users about the common questions and answers on the topic of water testing.

Did you know that if you drink water out of a private water supply, you should test your water source at least once each year and anytime the well is serviced or the water changes in look, smell or taste?

Did you know the contaminants that you should test for can be dependent on where you live in the state? The testing you need will depend on the actual source of your water, the historic and current land use practices, and your specific worries or concerns about your water and your overall health.

Please click on any of the questions linked below to view our guidance.

- Choose a topic -

Why should I test my water supply?

The groundwater that supplies your water well can become contaminated through natural processes and human related activities. In addition, Iowa is made up of unique geological settings that can create special construction, maintenance, and water testing needs.

Even if you believe that your well water is safe to drink, it's important to periodically sample and test your water to assess any health related concerns the water may create. The information you receive from the test will help you make informed decisions on well maintenance and water treatment. It will also help you determine if you need to call a certified well contractor or seek an alternative source of drinking water.

Groundwater can have unsafe levels of natural pollutants such as, such as arsenic, lead and radon, and modern lifestyle related contaminants like motor fuels, the solvents that help clean your clothing, homes and businesses, and chemicals that are beneficial for industrial and agricultural use. The degree to which a potential health threat may exist will depend on the amount and type of the contamination, the depth and protections incorporated in the well's construction, and how you use the water. In some cases, contamination of the water can be detected by sight, taste or smell; however, in most instances the contamination can only be detected through laboratory analysis of an untreated sample of the well water.

Back To Top

How often should I test my water supply?

At a minimum, we recommend bacteria and nitrate testing be performed at least once per year. If you live in an area where nitrate is high, you should also test for nitrite. Arsenic testing should be done at least one time on each drinking water well, or more often if you are in an area where other wells exhibit a change in arsenic levels. You may want to test your well more often than once each year depending on the problems you or neighboring well owners observe with your wells water (changes in color, taste, odor, hardness, corrosion, sediment, etc.). Depending on land use in areas nearby your well, you may want to test for additional contaminants and test more frequently to look for changes in contaminant levels.

There are other times when it's important to have your well water sampled and tested. These include when you have your well serviced or the pump repaired, anytime you have work done on your pressure system - like replacing a pressure tank and/or pressure switch, fixing water line leaks, adding new water lines to your property, adding or repairing yard hydrants or livestock watering devices, anytime a power outage lasts long enough for the water system to loose all pressure, anytime the well has sat idle for a long period of time without being used and anytime flood water has access to the well or areas nearby the well.

Back To Top

When is a good time to test my water supply?

You should have your well sampled and tested anytime you notice your water exhibits some type of change. Changes in your water quality can indicate there may be a problem with the safety of your drinking water. These indicators can be obvious like cloudiness, floating debris or sediment, and unusual odors and colors. In many cases, it may be difficult to know if your water is safe to consume because it appears normal. If there is any doubt that your water supply is safe to drink, we strongly recommend that you use an alternative known safe source for drinking water - like bottled water - until you have your water sampled and the testing provides proof that it's safe to drink.

In Iowa, wells are subjected to four distinct operational seasons - spring, summer, fall and winter. Each of the seasons can alter the manner in which you trouble-shoot well water quality problems. Although testing your well water can be done at any time of the year, some contaminants may be present only during specific conditions. Because of this, we recommend that the testing is performed during times when contaminants are most likely to be present.

Coliform bacteria and nitrate are most likely to be found during wet weather, when runoff and excess soil moisture carry contaminants into shallow groundwater sources or through defects that may exist in your well's design, borehole or casing. In general, these are the wet periods of late spring and early summer as well as the wet periods of the fall.

Pesticides used on lawns, gardens, or farm fields are most likely to be present in greatest concentrations soon after they are applied. With the exception of large chemical spills, it takes excess soil moisture to carry pesticides into the ground which makes late spring and early summer good times to test for pesticides if they are one of your concerns.

For naturally occurring contaminants like arsenic, fluoride, and radium, testing can be done at anytime because these contaminants are relatively stable in the groundwater.

Back To Top

What should I test for?

At a minimum, you should test your private drinking water supply for coliform bacteria and nitrate and nitrite. These contaminants are the common indicators used to provide basic information on drinking water safety. It's easy and inexpensive to test for these contaminants. When any of them are present above the Environmental Protection Agency's maximum contaminant levels (MCL), you should not drink the water without proper treatment.

We also recommend that every private well used for any drinking water purpose have at least one arsenic test performed so that the well user understands if arsenic is an issue with the water supply. More information on arsenic can be found on the State Hygienic Laboratory Arsenic Fact Sheet.

You may want to test for pesticides and other farm related chemicals if you obtain your water from a shallow well or your well is old, or if you obtain your water from a well finished in the shallower Karst bedrock regions of the state.

Pesticides are mostly modern chemicals that are used to control weeds and insects, and improve crop and turf production. They are applied on farms and in communities. You likely have a number of pesticides that you use routinely in and around your home. Atrazine is one of the most commonly found pesticides discovered during well water analysis. You can learn more about Atrazine in drinking water and health concerns that may be attributed to this chemical by visiting the CDC Atrazine Information web page. For more information on specific pesticide well water testing you may want to consider, please contact the State Hygienic Laboratory at the University of Iowa, 800-421-4692.

There are a number of other contaminants that you may want to test for based on your location in the state, the location of the well, the aquifer supplying your water, the age of the well (based on construction standards), and the land use or land history nearby your well. Contaminants like nitrate, arsenic, fluoride, radium, and lead are naturally occurring in some aquifers and may require specialized water treatment to reduce or eliminate the exposure risk. Certain locations may be susceptible to contamination from things like Volatile Organic Compounds (VOCs) such as gasoline, plastics, adhesives, dry-cleaning fluids, refrigerants, paints and solvents; animal waste like manure, carcasses and compost, or a number of emerging contaminants that may be linked to our modern lifestyle and activities.

These contaminants can end up in the groundwater due to local use and application, improper mixing, handling and storage, improper disposal, accidental spills, poor well construction, improperly abandoned wells, or the lack of natural protections in the local geology that normally provide protection to the local aquifers. If the natural protective features and barriers are not present in your region, the aquifers are more susceptible to contamination and you should test your water more often.

In the northeast region of Iowa, Karst bedrock features can allow surface water immediate access to the shallow groundwater. This makes the shallow groundwater more susceptible to surface contaminants. Wells in this part of the state require more stringent standards for well construction, increased water quality monitoring and increased maintenance of any drinking water treatment devices needed. For additional information on Karst terrain and water wells, please view our water wells in Karst areas web page.

If your water supply lacks adequate protections, is in poor repair, or utilizes an aquifer that interacts with surface water or very shallow groundwater, you should be especially aware of water borne diseases. Bacteria, viruses and protozoa are microorganism groups that contain pathogens that can cause waterborne diseases. For additional information on water borne diseases please see the Centers for Disease Control, Iowa Department of Public Health or your local county environmental health office.

Some private water systems may have corrosion issues that create the potential to release lead from the home's plumbing into the water in the pipes. Corrosion in house plumbing can be described as a dissolving or wearing away of metal caused by a chemical reaction between water and your plumbing. There are a number of factors involved in the extent to which lead enters the water, these include:

  • the chemistry of the water (acidity and alkalinity) and the types and amounts of minerals in the water,
  • the amount of lead it comes into contact with,
  • the temperature of the water,
  • the amount of wear in the pipes,
  • how long the water stays in pipes, and
  • the presence of protective scales or coatings inside the plumbing materials.

We recommend that private water systems have at least one lead test performed to help determine if corrosion may be an issue with the plumbing. Additional testing may be required if you change your water source or your method of water treatment.

For advice on what your well should be tested for based on your well location and aquifer please contact your local county environmental health office, the State Hygienic Laboratory, the Iowa Department of Public Health or the Iowa DNR.

Back To Top

Who can perform the water sampling?

Nearly everyone who can follow instructions can draw a water sample and submit it for analysis. Since the water analysis will normally be looking for health indicator bacteria, it's important that the water sampling be performed with great care so that the sample is not accidentally contaminated leading to a false indication that the water system is contaminated. If you are unsure about sampling procedures, call your local county environmental health office or your local Iowa Certified Well Contractor to obtain information on how you can have a water sample taken by experienced staff.

For additional information on how to correctly obtain a sample of your well water and submit it for testing, please refer to the State Hygienic Laboratory frequently asked questions web page.

Nearly all of Iowa's counties participate in the Grants-to-Counties Well Program. The Grants-to-Counties program can provide free water sampling and analysis to qualifying private drinking water systems. To find out if your county participates in the Grants-to-County Well Program or to arrange sampling of your water system, please refer to the list of County Environmental Health Sanitarians and contact the Sanitarian's office in the county where the well is located.
Back To Top

Can any lab perform the water analysis?

All water testing should be performed by Iowa DNR Certified Drinking Water Laboratories. These laboratories use accepted drinking water lab methods, employ highly trained staff who to perform the water analysis, and use DNR accepted standard operating procedures to help ensure your results are accurate.

To obtain additional information on well water testing or to order a water sample test kit, you can contact the State Hygienic Laboratory at the University of Iowa or any of the other Iowa DNR certified drinking water laboratory.

Back To Top

How do I interpret the laboratory report?

Each laboratory uses their own reporting form to detail the results of your drinking water analysis. Although the forms may look different, the information provided on each form should be nearly identical. When testing for coliform bacteria and nitrates, most lab analysis forms will state whether the water supply is "safe" or "unsafe" to use as a drinking water supply and state what the level of nitrate they found. You can also request that the laboratories provide you with a numerical level for the bacteria found in the sample if you make this request at the time the water sample is submitted and include the additional fee.

The goal of drinking water testing is to inform the well user if the water supply is safe for all consumptive uses. Testing "safe" means that the water supply is "absent" of coliform bacteria and fecal coliform bacteria, and the nitrate level is 10 mg/L or less when measured as nitrate-nitrogen or NO 3- N, or 45 mg/L or less when measured as Nitrate, Total Nitrate or NO3, and you have no reason to believe that there are other contamination concerns with the water supply. If you test for Nitrite, the result should be less than 1 mg/L.

When you have your water tested for other types of contaminants, the Environmental Protection Agency (EPA) maximum contaminant levels and guidelines should be used to determine if your water is safe to drink. The Water Systems Council wellcare® water testing information page offers additional guidance on well water testing and understanding your water analysis report.

The State Hygienic Laboratory at the University of Iowa is also a great resource and offers a number of documents for private wells. "Reading your water analysis report" is a document that can help you understand how to interpret private drinking water analysis reports based on their testing services.

Back To Top

What should I do if my water supply is unsafe to drink?

First and most important - stop consuming the water and find an alternative source for all of your consumable water needs. This can be bottled water, a neighboring water supply that is known safe, water from a public water supply like a neighboring town or city, or water that has been properly treated for the contaminants present in the water.

Then you should determine what the best short term and long term solutions are for your safe drinking water needs. Your options are to use bottled water for all consumable water needs, providing adequate water treatment at one or more drinking water taps, rehabilitation or renovation of the well or water system so that it provides safe water, connection to a known safe water supply, or replacement of your existing water supply.

In some cases, well related issues that can cause drinking water contamination are simple and can be remedied by adding protections to the existing well. Other times, the only good solution will be an alternative water supply. An Iowa DNR Certified Well Contractor can help diagnose your water issues and provide guidance on repairs or well replacement. Anytime you hire a contractor to work on your well or water system, the contractor must be certified by the Iowa DNR in the proper categories of well services. Certification ensures that the individual you hire meets a minimum level of knowledge and skill in the areas needed for your job. It's important to note that you should select your contractor carefully because even though a contractor may be certified by the state, they may not have the equipment or the experience to perform all well services.

To obtain additional information on water system rehabilitation, renovation, repair or replacement, please contact your local Iowa DNR Certified Well Driller or Certified Pump Installer.

To learn more about ownership of a private water supply, please look at our private well consumer information booklet.

Back To Top

Can I use a water treatment device?

Water treatment devices are commonly used to produce safe drinking water. The type of device that you need and the installation, maintenance, and monitoring of your treatment device will depend on the type of contamination that you have and the type of device used for treatment. Some contaminants require very specialized water treatment. Even if you already have some form of water treatment, you may not be reducing or removing all contaminants that can cause short or long term health issues.

One last important point to consider is that all water treatment devices require ongoing maintenance, monitoring, and testing to ensure that they are properly treating the water. The maintenance intervals and cost of maintenance vary with each specific treatment device. Make sure to inquire about ongoing maintenance schedules and the true cost of ownership when you discuss your water treatment options.

All drinking water treatment devices that are sold in Iowa must undergo third-party testing and be registered under a program administered by the Iowa Department of Public Health (IDPH). For additional information on water treatment system registration, please contact the IDPH at their home drinking water treatment system registration web page.

To learn more about water treatment device options, please look at the information on the following links:
State Hygienic Laboratory at the University of Iowa information booklet Well Water Quality and Home Treatment Systems

National Sanitation Association's Home Water Treatment Devices guidance web page.

Water Systems Council Home Drinking Water Treatment Systems web page.

Iowa Department of Public Health lists for registered water treatment systems.
General water treatment devices
Additional information regarding treatment of Arsenic
Back To Top

Additional Resources

- For more information contact -

Russell Tell, Environmental Specialist Senior
Wallace State Office Building
502 E. 9th Street
Des Moines, IA 50319-0034
(515) 725-0462 or by Fax: (515) 725-8202