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bacteria, salmonella, pathogens, water testing lab wisconsin cdc, dnr wdatcp
Are you one of the nearly 1 million well water owners or users in the state of Wisconsin? Find out why you should be testing regularly for pathogens like Coliform, and E.Coli.

There are over 900,000 private well owners & well users in the state of Wisconsin. Each one is using their well water for their family’s cooking, cleaning, bathing, laundry, garden watering, and more. Even with Wisconsin’s stringent water quality laws & regulations, they still can be at risk of falling seriously ill from Coliform & more specifically, E.Coli bacteria. We hope to give some info that will keep you, your friends, and your family a little bit safer when it comes to taking care of your private water well.

Municipalities are required to test their water supplies regularly, to ensure the water is safe for residents to drink. Since there is no requirement for you to test a private well except for bacteria (when it is first drilled), or when the well’s pump is changed, you personally are responsible for making sure your water is safe. Let US Water help you monitor, mitigate risk, and when a problem pops up, we’ll be there to fix it too.

What should be tested for?

The decision on what you should test for, in your well, should be based on the types of land-uses nearby your water well. In this write-up, we’ll describe a very common contaminant found in private wells – Coliform / E.Coli bacterium. This information should help you decide when to have your well sampled by US Water, and how often.

What is Coliform and E.Coli bacteria and how does it get in my water?

Coliform bacteria live in the soil, on plants & vegetation, and throughout surface water. You’ve probably heard of the strain of coliform bacteria commonly found in the intestines of warm-blooded animals and their feces, which is called E.coli. Some strains of coliform bacteria can survive for long periods in soil and water and can be carried into Well Casings by insects. As if bugs didn’t cause enough problems!

Usually, Coliform bacteria that get washed into the ground by rainwater or melting snow are filtered out, and get stuck in the soil, as the water seeps through. However, the bacteria does sometimes get into water supplies through fractured bedrock, cracked well casings, poorly-sealed caps, and through runoff into sinkholes. Coliform bacteria are the most common contaminants found in private water well systems. In 1994 a survey in Wisconsin found Coliform bacteria in 23% of the wells tested and E.coli in 2.4% of the tested wells. Not a very exciting statistic to read.

The Good News & The Bad News

The good news is that most coliform bacteria do not cause serious illness.

The bad news is that their presence in a water test does indicate that there has been a breach in the well water system.

It is worth noting, since E.coli bacteria are found in fecal material, they are often present in samples with other bacteria, viruses and parasites that can cause flu-like symptoms such as nausea, vomiting, fever & diarrhea.

US Water & DNR Recommendations

The Wisconsin DNR recommends Private wells get tested at least once a year for bacteria, by a laboratory like US Water, LLC’s ‘US Water Lab’, that performs an E.coli test when total coliform are present. It is always recommended that you test again if there is a change in the taste, odor, color, or appearance of your water.

The coliform test is one of the most important tests you should have done on your well water. However, bacteria are only one of many possible contaminants. A negative bacteria test is good news, but does not mean your well is free of other contaminants.

Get in touch with US Water for your water testing needs.

Information sourced from Official Wisconsin DNR Website


Matt Zastrow
Matt Zastrow

Laboratory Manager at US Water. 10 years of experience in water testing. WI DNR & CDC Elite Certified.

About US Water:

Since June of 2000, US Water has provided Wisconsin homes & businesses with expert solutions to their water problems. 


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