Water Testing:  Why and How to Do It &
What Does It All Mean?

What is in your water and what does it mean?


bulletSubstances that Can Be Tested For
bulletWater Testing Laboratories


bulletDrinking Water Quality Law
bulletWater Sampling Procedure


bulletWater Test Interpretation

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You cannot see, taste, or smell nitrate or many other substances that may contaminate your water.  The only way to know what is in your drinking water is to have it tested.  If you receive municipal water, then your municipality is required by law to regularly test and keep regulated substances below the drinking water maximum contaminant levels (MCL). 



However, private well owners are responsible for testing their own water to make sure that it is safe to drink and use.  Water from private wells should be tested annually for at least nitrate and coliform bacteria.  Other substances, both inorganic and organic, may also be tested for. The sampling process is easy and relatively inexpensive, yet less than 5% of the 700,000 wells in Wisconsin are tested annually.  The challenging part is interpreting the water test results and figuring out what to do.

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Drinking Water Quality Law

The federal Safe Drinking Water Act (1974) was established to protect the quality of drinking water in the United States.  This law applies to all water that may be used for drinking, whether the source is surface water or groundwater.  This Act required the EPA to set water quality standards called, Maximum Contaminant Levels (MCL), to protect human health.  Thus far, about 82 substances have MCLs.  Wisconsin DNR has adopted these MCLs in the Wisconsin Drinking Water Standards: NR 809- Safe drinking water.   

MCLs are determined for substances that have the potential to cause short or long term health impacts.  Secondary standards are set for substances that cause aesthetic problems such as bad odor or taste.   In addition in Wisconsin, Preventative Action Limits (PAL) are set for each regulated substance.  PALs are "early warning signs" that water quality may be in jeopardy.  MCLs legally only apply to public water supply systems, however private well owners are highly encouraged to use these limits as a guide for their own water quality. 

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Substances that Can Be Tested For

Every year, well water should be tested for at least coliform bacteria and nitrate.  However, a water sample can be tested for a variety substances all at one time.      Some labs, like the ETF Lab,  have a "homeowners package" that includes tests for nitrate, coliform bacteria, pH, total hardness, chloride, conductivity, and alkalinity.  From these test results the corrosivity is determined.  The ETF Lab also offers a "homeowners metal package" that includes tests for arsenic, calcium, copper, iron, lead screening, magnesium, manganese, potassium, sodium, sulfate, and zinc.  Other substances or conditions that can be tested for in water include multiple pesticides, chemical oxygen demand, VOCs (volatile organic compounds), and others.  

The above tests were chosen to identify the most common problems in Wisconsin.  Other areas may have other testing concerns.


The DNR website and ETF website  provide more information about these and other water tests.

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Substances found in groundwater and water can be classified a few ways:

bulletinorganic vs. organic
bulletnaturally occurring vs. human-induced (See table below.)
bullethealth risk vs. aesthetic problem  vs. indicator test (See table below.)

Classifications for Substances Found in Groundwater in Wisconsin

  Naturally Occurring Contaminants Human Induced Contaminants
Health Risk
bulletArsenic (generally not prevalent in Portage County)
bulletColiform Bacteria
bulletPesticides (atrazine or triazine)
Aesthetic Problem
(bad taste, odor, color)
Indicator Test
bulletSaturation Index


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Inorganic Substances in Water

Inorganic substances include various mineral substances such as iron, nitrate, and others.  Some naturally occur while others are introduced by humans.  Some cause health problems such as arsenic and nitrate.  Some can cause taste and odor problems such as iron and sulfur.  The ETF website contains a list of inorganic compounds for which they test.

Organic Substances in Water

Organic compounds in water are more chemically complex than inorganic substances and gerneally more expensive to test for.  Organic compounds of concern in drinking water include cleaning solvents, gasoline, pesticides, and compouns formed when water is disinfected with chlorine.  The ETF website contains a list of organic compounds for which they test.

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Naturally Occurring Contaminants

Naturally, soft rainwater becomes "hard water" when it passes through rock or soil that contains calcium or magnesium.  For example, dolomite rock contributes calcium and magnesium to water.  Conversely, the central sands area of Wisconsin has much lower hardness.  The geology within the recharge area can also contribute other substances to water such as iron and sulfur.

Human-Induced Contaminants

Watershed boundaries usually determine the recharge area for wells.  Since water passes from the land surface to the water table, activities on the land surface can affect groundwater quality.  Fertilizers, pesticides, household cleaners, human and animal waste, underground storage tanks, as well as hazardous wastes can contaminate groundwater.   

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Health Risk

Substances that have the potential to cause short or long term health impacts are considered a health risk.  These risks are determined through scientific toxicity studies usually conducted on laboratory animals, and humans in the workplace.  Based on these studies, researchers determine contaminant concentrations that should not cause human health impacts.  Wisconsin uses "drinking water standards" and "health advisories" to place a ceiling on the amount of contaminant in water.  Another term used by the EPA is "maximum contaminant level (MCL)".

Aesthetic Problem

An aesthetic problem is a non-hazardous nuisance such as bad taste, odor, or color.  Aesthetic problems also include chemicals that cause corrosion or staining.  For example, iron in water can taste and smell bad, as well as cause a red-brown stain.  Manganese in water causes black stains.  These contaminants are also called, "secondary contaminants" by the EPA.

Indicator Test

Indicator tests are used to indicate or highlight a possible problem. An indicator is a substance/condition measured to show the condition of the water with respect to the presence of a particular material.  For example, the saturation index measurement indicates the corrosivity of water.

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Basic Water Sampling Procedure for Homeowners

 The sampling process is usually simple for most homeowners.  However, some specialized tests require a more complicated collection process that might have to be done by a professional.

  1. Stop by a water testing laboratory (listed below) or telephone, and request a water sampling kit.  The kit comes in styrofoam container that includes a plastic bottle and an information sheet with directions. 

  1. Be sure to read the directions inside your kit, because sampling procedures can vary depending on the type of test being done.  Some tests require a special bottle.
  1. Be sure to remove any screens and home filter systems.  A non-swivel faucet must be used when testing for bacteria.
  1. Heat the tip of the faucet with a lighter or torch until it is hot.  Be sure to only contact metal parts with the flame.
  1. Let the cold water run for about 5 minutes.
  1. Carefully remove bottle and cap without touching the insides.  Fill the sample bottle leaving about 1/2 inch air space at the top, replace cap, and place in the styrofoam container.
  1. Fill out the information sheet to the best of your ability. Be sure to include the sampling date, time, and legal description.  Place the completed sheet inside the styrofoam box. 

  ETF Water Sample Information Sheet.  
(The ETF sheet looks a little intimidating at first, but just take it one blank at a time.)  


  1. Enclose a check made out to the water testing laboratory for the appropriate amount.  Prices vary, so check with the lab.
  1. Drop off the styrofoam container to the water testing laboratory during hours of operation, or mail it directly to the lab.  Water being tested for bacteria must be turned into the lab within 36 hours from the time of collection.
  1. Water test results and an interpretation sheet will be returned to you in the mail.

Private well owners should test their water every 15 months for coliform bacteria. Nitrate should be tested every 15 months, if you live close to agricultural crops or feed lots, or if the water had levels close to or exceeding the 10 ppm MCL.  Testing every 15 months allows you to look at seasonal changes.  The frequency for other substances to be tested varies from annually to once every 10 years.

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Certified Water Testing Laboratories

Two agencies certify water testing laboratories.  The Wisconsin Department of Natural Resources (DNR) certify labs that test for contaminants such as nitrate, pesticides, metals, and VOCs (volatile organic compounds).  The Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) certifies labs that test for bacteria.

Portage County has one certified lab for testing water samples:

Environmental Task Force Laboratory  (ETF)
University of Wisconsin-Stevens Point
College of Natural Resources, Room 200
Stevens Point, WI 54481
715-346-3209 or toll free 877-ETF-TEST
email: dsisk@uwsp.edu 
directions: map of campus

Hours of Operation:

bulletMonday-Wednesday, 7:45am- 3:30pm for bacteria testing, 
bulletMonday-Friday, 7:45-3:30pm for other water tests

Certified to test for bacteria and organic and inorganic contaminants such as heavy metals, nutrients, pesticides, polynuclear aromatic hydrocarbons, polychlorinated biphenyls, and volatile organic compounds.

In addition to this lab, the Wisconsin DNR maintains a complete list of certified water testing laboratories for the entire state.

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Water Test Interpretations

What do the test results mean?  An on-line brochure, Interpreting Your Drinking Water Quality Results:  Identifying Problems and Solutions, explains the meaning of each test in the "homeowners package," and helps identify problems and solutions.  This brochure will be included with your water test results.

For further questions or information, contact Chris Mechenich at the Central Wisconsin Groundwater Center at 715-346-4276 or cmecheni@uwsp.edu or Mike Carder, Environmental Health Supervisor at 715-345-5770 or carderm@co.portage.wi.us

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bulletDrinking Water Education Program for Wisconsin Counties:  About the program and upcoming program dates.
bulletHigh Nitrate in Your Drinking Water:  What do you do?
bulletGroundwater Laws and Regulations

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Nitrate:  sources  |  explanation  |  impacts  |  PC levels  |  in drinking water  | actions

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