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Water Quality

Testing and ReportingSun Prairie Utilities Annual Water Quality Report.

Sun Prairie Utilities checks and monitors each well location every day. Pumpage from each well is tracked and logged, and chemical levels are tracked and logged. Water samples are tested in accordance with Wisconsin Department of Natural Resources regulations and requirements. DNR testing results are provided to our customers annually with the Sun Prairie Water Quality Report (click here to read it).

Chlorine and Fluoride

Chlorine is used to disinfect our water and minimize the risk of microbial contamination by bacteria or viruses. The average free residual chlorine concentration in the system is maintained at 0.3 parts per million (ppm) (also stated as milligrams per liter, mg/L). Chlorine is added to drinking water systems to assure that microbial organisms such as bacteria and viruses cannot survive in the water. The chlorine levels are not a health concern and, in fact, are established to prevent health risk from bacteria and viruses. If customers experience a persistent and excessive odor or taste of chlorine in their drinking water, they should call the utility at 837-5500, and the report will be investigated.

Fluoride is added to our water to improve dental health and reduce tooth decay. The average fluoride level in our water is currently being set at 0.7 milligrams per liter, based on recommendation of the U.S. Department of Health and Human Services. The Centers for Disease Control and Prevention (CDC) has recognized water fluoridation as one of ten great public health achievements of the 20th century.

Lead and Copper

Sun Prairie's ground water supply does not contain significant amounts of naturally occurring lead or copper. The naturally corrosive nature of water, however, can dissolve or corrode lead and copper through contact with water service lines, interior pipes and plumbing fixtures. Lead in drinking water can cause a variety of adverse health effects:

  • In babies and children, exposure to lead in drinking water above the action level can result in delays in physical and mental development, along with deficits in attention span and learning abilities.
  • In adults, kidney problems or high blood pressure could result if water with high levels of lead is ingested over a long period of time.

Read the WI DNR pamphlet, Lead in Drinking Water, Copper in Drinking Water for more information.

Resource:  How to identify if you have a lead service pipe.

The Environmental Protection Agency (EPA) requires that the levels of lead and copper in drinking water be limited. Sun Prairie Utilities tests and monitors 36 specific properties throughout the city annually for levels of lead in its water. These properties represent a cross section of various locations and decades of construction. The SPU 2017 system average is 2.05 parts per billion (ppb) as compared to the EPA action level currently set at 15 ppb.

If you don't know whether your tap water contains lead you should have your water tested by a certified lab. Proper sampling is required to obtain a valid result. (Note: A single test for lead level in drinking water may not be representative of the level at all times or of the average level over time.)

You can contact the one of the following certified laboratories to get lead sampling procedure information:

  • State Lab of Hygiene, 2601 Agriculture Drive, Madison, WI 53707.  Call (608) 224-6202
  • Public Health-Madison & Dane County, 210 Martin Luther King, Jr. Blvd., Madison, WI 53709.  Call (608) 266-4821

Resource:  Environmental Protection Agency - Lead Fact Sheet


Chromium is a metallic element found naturally in rocks, soil, plants, and animals including humans. It occurs in the environment and in drinking water sources in two principal forms:  chromium-3 and chromium-6 (also called hexavalent chromium or hex chrome). The sum of all chromium in a sample is called total chromium.

Chromium-3 occurs naturally in many vegetables, fruits, meats, and grains and is an essential dietary nutrient, while the more toxic form, chromium-6, is generally produced by industrial processes. Chromium-6 occurs naturally in the ground but may also enter drinking water sources, including groundwater, from historic leaks and industrial waste sites.

Chromium can change from chromium-3 to chromium-6, and vice versa, depending on the chemical and physical environment.

Resource:  Environmental Protection Agency – Basic Information about Chromium in Drinking Water


The sub-rock beneath Sun Prairie soil is primarily limestone. This is a contributing factor to the “very hard” water of our ground water supply. This water contains 22 grains of hardness per gallon. There are no harmful health effects associated with these minerals (in fact, some believe they are beneficial), but measuring them does provide a guideline as to how water use may be affected. For example, hard water does result in more scale buildup and you need to use more soap and detergents. If you choose a water softener, it's recommended that a separate, unsoftened supply of water be kept for cooking and drinking. Ion exchange water softeners remove hardness by replacing the calcium and magnesium with sodium salt. City of Sun Prairie Chlorides and Water Softener statement.

Also, when you buy a new appliance, such as a dishwasher, the manufacturer often makes reference to water hardness. This is because hard water can cause automatic dishwashers to leave film on dishes and build-up of minerals on mechanical parts.  It may also cause washing machines to leave residue on articles of clothing and scales that clog water pipes or foul appliances such as water heaters.


Resource:  Sun Prairie Water System Municipal Codes Title 13 - Public Services