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Environmental Health:  Private Drinking Water Well Owners


Drinking Water Well Owners

Congratulations!  You have your own private water supply.  The water tastes great, and you have no monthly water utility bills to pay.  You also have no one watching out to make sure that your water supply stays safe and sanitary, so that job is up to you.  Managing your water supply is not difficult, but you need to be aware that there are times of the year and specific conditions that can contribute to contamination of the water well.

What can possibly go wrong?

What can go wrong?  Well, spring can arrive!  With Spring in the Northern Rockies comes snow melt and rising rivers and streams.  During the spring of the year, it is not uncommon for drinking water wells to become contaminated, because as rivers rise and fall, so does the groundwater.  It is during this time that contaminants can be carried into the well.  We strongly recommend that private water wells be tested just after spring run-off.  Some other common problems we see include the following:

Do I need to test my water? - YES!

When should I test my water?

What does water testing tell me?

A basic water test checks the water sample for the presence of total coliform bacteriaTotal coliform bacteria are common in the environment, but should not be found in water supplies or sources. For this reason they are used as indicator organisms. Fecal coliforms are a type of coliform bacteria found only in the intestines of warm-blooded animals. They can not reproduce or survive long outside of this environment. If a water sample is found to contain E. coli or fecal coliform bacteria, the water has either been in direct contact with raw sewage or has been in contact with something else that has been in direct contact with raw sewage.  In either case, the presence of total coliform with or without fecal coliform in the water sample is considered "contaminated."

Will contaminated water hurt me?

Typically, wells contaminated with low levels of total coliform bacteria may not taste bad or look different.  In fact, if you have been drinking water from a contaminated well for a long period of time, you may not have any health symptoms.  Visitors, young children, the elderly, pregnant women or folks with health problems may become ill from drinking the water.  Symptoms usually include stomach ache and/or diarrhea.

Wells contaminated with fecal coliform bacteria, including E. coli may cause more severe stomach cramping, diarrhea and sometimes vomiting.  If your water is contaminated, you can boil it for three minutes and let it cool before drinking it.  Boiling will kill the bacteria.  Store the boiled and cooled water in the refrigerator.

How do I make my well safe?

The process of killing the bacteria in your well is called "disinfection."  For wells with high numbers of bacteria, more than one disinfection procedure may be required.  Disinfection is typically done by removing the well cap and pouring a solution of household bleach and water down the well casing.  Then the well cap is replaced and water is run through all the water piping in the home.  Please see the Well Disinfection Sheet in Word or PDF form.

How do I know my well water is safe?

The only way to know your well water is safe is to have a sample of the water tested.  The Missoula City-County Health Department water lab is certified to perform water tests.  For information about our lab costs, see the Water Lab Fees link.

Other water labs are available locally, too.  See the Yellow Pages under Water Analysis for area labs.

What if I have other Water Well concerns or questions?

There are a number of resources for private water well owners on the Internet.  Another very good source of information is the County Extension Service.  There are videos you can watch and download.

What if I want to check for chemicals in my water?

The Montana State Environmental Lab is set up to run many tests: it can do chemical and metal screening, as well as biological and hardness testing for water.  Missoula City-County Health Department carries of supply of water sample bottles from the state lab for your convenience.