Coliform Contamination in Well Water: Causes and Prevention

Elimination of coliform bacteria from a private water well is an essential part of providing healthy water for a household, especially if any member is immunocompromised. Even the health of any animals in the household depends on the purity of the water. In this article, we will explain exactly what any well owner needs to know to detect or eliminate coliform contamination of their well. 

About Coliform Bacteria and the Problems They Cause

There are several bacteria in the group that are referred to as “coliform.” The word itself derives from the word “colon,” since coliform bacteria are commonly found in the colons of humans and animals. 

Some coliform bacteria are actually harmless. Other types of coliform bacteria cause illness that can be severe or even fatal. That is why it’s so important to test private well water for coliform bacteria. 

The other reason it’s vital to test a private water well for coliform bacteria is this: Even if the specific coliform bacteria are not harmful, their presence in a well is an important indicator of contamination by human or animal fecal matter. The other bacteria or pathogens introduced by that fecal contamination could well be very damaging or even fatal. 

Types of Coliform Bacteria Found in a Well

A test for coliform bacteria will be positive if any of these microorganism are detected:

  • Enterobacter aerogenes
  • Escherichia coli
  • Campylobacter coli
  • Klebsiella pneumoniae
  • Citrobacter freundii
  • Serratia
  • Hafnia
  • Yersinia

The bacterium Escherichia coli (E. coli) is the most well-known of these bacteria. That’s because most people have read news releases stating that certain agricultural products have been found to be contaminated with E. coli. The World Health Organization noted in 2006 that E. coli is rarely found in water that is not also polluted by feces. Therefore, the presence of E. coli is a sign that agricultural products may be contaminated by fecal matter. 

Detecting coliform bacteria is easy and inexpensive. For that reason, a test for coliform bacteria is a common safety test for drinking water sources. Trying to test a water supply for a long list of other possible bacterial contaminants would get very expensive. 

Bacteria That May Be Present with Coliform Bacteria

The presence of coliform bacteria makes it more likely that the following disease-causing bacteria may also be present:

  • Shigella
  • Salmonella
  • Vibrio cholerae

A simple test for coliform bacteria will serve as an indicator that there is a problem with the well that requires disinfection and may require repair or even relocation of the well. 

Symptoms of Coliform Bacteria Contamination in Drinking Water

As noted, many but not all coliform bacteria are harmless. Even within one type of coliform bacteria—E. coli, for example—some strains are relatively harmless but one strain can cause severe illness. Identifying the exact strain in a sample of water would be a lengthy and expensive process. That’s why a simple and easy test for coliform bacteria or E. coli is the way well owners determine if the water has been contaminated. 

The following types coliform bacteria are known to cause illness: 

  • Campylobacter coli: Mild self-limiting illness of the gastrointestinal tract
  • Enterobacter cloacae: Gastrointestinal illness
  • Escherichia coli: Gastrointestinal illness that can cause kidney failure, urinary tract infections
  • Klebsiella pneumoniae: Pneumonia or urinary tract infections
  • Hafnia alvei: Pneumonia, urinary tract infections, peritonitis

Infections outside the intestines generally only occur in immune-compromised persons. The best way to eliminate the possibility of intestinal or outside-the-intestines infection caused by one of the coliform bacteria is to fully sanitize the water well and prevent future contamination. 

Non-Coliform Bacteria Can Also Cause Illness 

Diseases caused by non-coliform bacteria that are likely to be present in the same well with coliform bacteria:

  • Shigella: Mild self-limiting gastrointestinal illness plus bloody diarrhea, stomach cramps, fever
  • Salmonella: Mild self-limiting gastrointestinal illness, stomach cramps, fever, diarrhea
  • Vibrio cholerae: Gastrointestinal illness accompanied by watery diarrhea, dehydration, vomiting, muscle cramps

How Are Coliform Bacteria Getting into Drinking Water Wells?

Drinking water wells are constructed in a way that prevents insects, animals, surface water and fecal matter from entering the water supply. However, improper location, deterioration or damage can impair the sanitation of a well. 

If contamination is detected, here are some of the points that must be checked to determine the way coliform bacteria or other pathogens make their way into the well. 

  1. Well cap is missing or damaged. The well cap should seal tightly, preventing surface water, plant debris or animals from entering the well. 
  2. The wellhead is too close to the ground. Or it could be even with the surface or underground. The wellhead should be located at least 12 inches above the surface of the ground. Eighteen inches is better. 
  3. The well is located in a depression that collects surface water. Or it could be located on a slope so that water flows toward it. 
  4. The well casing has cracks or holes in it. The well casing is designed to seal out surface water. It should extend far enough into the well that any water seeping into the well’s water supply has been thoroughly filtered through the soil around the well. 
  5. The casing was not properly sealed. The space between the casing and the surrounding rock must be sealed to prevent water from flowing down the side of the casing. This sealing generally involves pumping cement or bentonite into this space.  
  6. A flood has inundated the area of the well with bacteria-laden water. If there is a significant flood, even a well in good repair can be contaminated. 
  7. There are leaking septic tanks in the area. Old abandoned septic tanks can leak contaminants. Newer septic tanks that need repair can also leak contaminants that make their way into the water supply. A well should be located at least 50 feet from a septic tank. It should be located at least 100 feet from the drainfield. 
  8. The pump was contaminated during installation or repair. If it was set on the ground during this process and was not disinfected before installation, it can introduce coliform bacteria into the well.
  9. Runoff from animal waste enters the well. This could occur in the event of very heavy rain or a flood if the wellhead is too low. A flood can also contaminate groundwater with animal waste which then makes its way into the well. Animal waste can come from feedlots, pastures or kennels.
  10. There is vegetation, debris or a woodpile near the well. This encourages the presence of insects that may be attracted to the water. These insects can carry coliform bacteria into the well. 
  11. The aquifer supplying the well could have an undesirable composition. If it’s composed of coarse gravel or sand, it may not not properly filter bacteria and other contaminants. 
  12. There is an old, unused well on the property. If it’s not properly plugged when it goes out of service, it could contaminate groundwater. 
  13. The well is near a river, stream, pond or lake. Groundwater can be contaminated by bacteria in the nearby body of water. 

Eliminating the Source of Coliform Contamination

Looking over the list above, it is easy to see that some of these sources of contamination involve getting a well or wellhead repaired by a professional well service. A repair like a wellhead that is too low is a fairly simple repair. Repairing the well cap is also simple. Repairing the casing of a well is a much more extensive operation. 

Plugging an unused well or an abandoned septic system should also be done by a professional. 

In some of these situations, there is no solution but a relocation of the well. For that reason, it is important to engage an experienced and competent professional well drilling company when you are having a well constructed. Proper location and construction will prevent many of these problems from ever coming up. 

Test Your Water for Coliform Bacteria Contamination

Every well owner should test their water annually, checking for coliform bacteria, sediment, total dissolved solids, alkalinity, metals, harmful levels of minerals or metals, and many other characteristics or contaminants. 

A test that is positive coliform bacteria should be followed by a thorough disinfection. Another source of drinking and cooking water should be utilized until disinfection has been done and a follow-up test shows that there is no further contamination. 

A few of the causes of coliform contamination can be remedied by the well owner, such as clearing debris from around the well or checking that a well cap is in good repair. Most of the other causes require a professional inspection. An annual water test is an essential tool if a well owner is to keep their water supply clean, pure and healthy. 

When to Test Your Water for Coliform Bacteria

While every well should be tested annually, there are other times that call for an additional test: 

  • When a new well has been constructed
  • When a well is returned to service after being idle for a few weeks
  • The odor, color or taste of the water changes
  • Someone in the household experiences gastrointestinal illness
  • There has been a flood in the area
  • A new baby, older person or someone who is immunocompromised is added to the household
  • Any part of the well has been opened for service
  • A neighbor has suffered water contamination
  • There has been a flood or other inundation of surface water
  • There has been construction or extensive landscaping nearby

How to Remove Coliform Bacteria From Your Water

Every well should be disinfected at least annually. Of course, if a water test reveals the presence of coliform or other bacteria, disinfection should occur immediately. Some websites advise well owners to dump household bleach into their well to kill bacteria. This is not the best way to disinfect a well because household bleach is heavier than water. It can sink to the bottom of a well or get trapped in pockets of the home’s plumbing. In one case, a well owner who tried to disinfect his well with household bleach flushed thousands of gallons of water through his system, trying to eliminate the smell of bleach. He was unsuccessful.

Instead of household bleach, use a calcium hypochlorite disinfectant made specifically for well disinfection. This substance has been approved by the Food and Drug Administration for private well disinfection. 

There is another reason to avoid chlorine household bleaches for well disinfection. Chlorine products interact with organic contaminants that may be in your well, such as plant matter. Chlorine plus organic contaminants can create trihalomethanes, cancer-causing chemicals. Using a calcium hypochlorite disinfectant avoids creating these chemicals while thoroughly disinfecting your well and flushing out thoroughly and easily. 

Preventing Future Coliform Contamination of Your Well Water

Diligent maintenance of a private water well, annual testing and proper disinfection are the best ways to prevent coliform contamination of your water supply. Every positive coliform test should be followed with a close examination of the well components to rule out any of the causes of contamination listed above. Otherwise, the contamination can recur. 

There are also advanced technologies such as ultraviolet disinfection, ozonation or special types of filtration that can eliminate or reduce coliform bacteria contamination. Carbon filters and water softening systems will not remove bacteria. Reverse osmosis is not recommended as a method of removing coliform bacteria as the microorganisms can cause the membrane in the filter to deteriorate. Pinhole leaks in this membrane will allow bacteria to pass through. 

For most well owners, the following steps are sufficient to maintain a healthy water supply:

  1. Annual testing for coliform contamination plus additional testing as indicated 
  2. Access to the correct disinfection kits and knowing the right way to use them
  3. Regular examination of the external components of the well and knowledge of how to maintain them
  4. Having a well expert you can rely on for timely, thorough inspections and repairs

How to Obtain Accurate Testing and Disinfection Kits

ETR Laboratories supplies thousands of private well owners with fast, accurate water tests and calcium hypochlorite disinfectant kits that eliminate dangerous bacteria. Each disinfection kit comes with a follow-up test to verify that all bacteria have been eliminated. Let ETR Labs help you maintain a healthy well, year after year. Check out our Well Chlorination Kit now.