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Central Wisconsin Groundwater Center - Water Testing and Private Wells


Frequently Asked Questions

Question Answer For More Information
Why should I test my well water? ​Most health related contaminants cannot be seen, tasted or smelled.  The only way to determine the safety of your well water supply is to have the water tested.  Water testing should be a regular routine for private well users since water quality can change over time.  Tests for Drinking Water from Private Wells
How do I know what to test for?  Some tests like bacteria and nitrate should be done on a regular basis.  There are many other tests to consider that may be specific to nearby land-use activities or naturally occcuring contaminants in your local area.  ​

Tests for Drinking Water from Private Wells

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Where can I test my well water? ​To ensure that the results are reliable, it is recommended that water samples be sent to a state-certified testing laboratory for analysis.  Laboratories have special bottles and collection procedures.  The Water and Environmental Analysis Lab is state-certified to test for a number of tests important to private well owners.  Whichever lab you choose, contact a lab first to request a test kit and instructions on how to collect and submit a sample. 

Water and Environmental Analysis Lab

List of other certified water testing labs for coliform bacteria and nitrate testing

Locate a certified water testing laboratory for other contaminants of concern

How can I find out more about the construction of my well?
Well construction can influence well water quality.  Knowing your well construction can be useful when trying to understand water quality or find solutions to problems. Starting in 1988 all newly drilled wells will have a Wisconsin Unique Well Number (WUWN). If you have this number, finding well construction information can be done online. If your well is older than 1988, you will have to contact the WGNHS to perform a search for a small fee.  

How to request a well constructor's report

If you have a WUWN you can search online here.

What to do if a well test shows problems with your well water quality? Finding solutions to well water quality problems is in the best interest of the homeowner because of health concerns related to drinking water and the value of the well in the overall price of a home.  When water quality problems arise it can be frustrating since there is no one solution to all water quality problems.  The following publication may help assist well users in deciding on options to improve their water.  ​ Improving your private well water quality
What can I do to protect groundwater?
Groundwater is a local resource.  What land-use activities we allow to take place and how carefully those activities are preformed will determine groundwater quality in the area around our homes.  Water is a shared resource, we all must do our part to help keep our groundwater supplies safe. 

Better Homes and Groundwater

Maintaining your home well water system


Common Water Quality Problems 



Arsenic is a naturally occurring element found in soil and rock and under certain conditions can be released into groundwater and enter wells. Elevated levels of arsenic have been found in a number of wells throughout the state with the majority of these being reported in northeastern Wisconsin. Because of an increased risk of health complications due to arsenic in drinking water there is a drinking water standard of parts per billion (or sometimes reported as 0.010 mg/L).

For the most up to date information on arsenic in drinking water visit the Wisconsin DNR arsenic page.


Coliform Bacteria

Coliform bacteria are one of the most common problems in Wisconsin's private wells.  As many as 25% of the private well samples tested annually are unsafe because of the presence of coliform bacteria.



Increased levels of copper in drinking water is caused by corrosive water and the dissolution of copper plumbing.  Levels of copper in drinking water greater than 1.3 milligrams per liter (mg/L, also called parts per million or ppm) may cause digestive problems.


Hardness and Water Softeners

Hard water is caused when water comes in contact with rocks such as limestone and dolomite which contain calcium and magnesium.  While hard water is not a health concern, excessive amounts of water hardness can cause lime or scale build-up in pipes and reduce the effectiveness or life of your plumbing.  Water softeners are a common and effective treatment device for homes with water hardness problems. 



Although iron in drinking water is not a health concern, concentrations over 0.3 milligrams per liter can cause undesirable taste and discoloration problems.  Water high in iron are also susceptible to iron bacteria.



Not naturally occurring in Wisconsin groundwater at levels of health concern.  Found in water supplies with lead solder or pipes, especially when water is soft or corrosive.  While lead is never desirable, concentrations greater than 15 micrograms per liter (15 ug/L also known as parts per billion or ppb) can cause brain, nerve, and kidney damage, especially in young children.


Nitrate Nitrogen

Nitrate nitrogen (commonly referred to as nitrate) is one of the most common contaminants found in Wisconsin groundwater.  Approximately 12% of private wells in the state exceed the safe drinking water standard of 10 milligrams per liter (mg/L, also called parts per million or ppm) for nitrate nitrogen.



A pesticide is any substance used to control or repel unwanted pests and includes insecticides, herbicides, and fungicides.  When pesticides are spilled, disposed of, or applied on the soil, some amount can be carried into groundwater and your private well.  There are many pesticides and the effects of many pesticides on health are not known.  If you suspect contamination or live close to areas where pesticides are used it is always a good idea to have your water tested.  



Volatile Organic Chemicals (VOCs)


Other Useful Extension Bulletins on Drinking Water Issues


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