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Home » Water Education & Testing » Coliform Bacteria in Well Water Guide

Coliform Bacteria in Well Water Guide

By: Craig Smith
Last Updated:
coliform bacteria in well water

If your home is supplied by well water, then one of your biggest concerns should be bacteria being found in that water and even more specifically coliform bacteria.

Don’t panic if you come to find that your well water has been contaminated with coliform bacteria.

This is not a death sentence for your well by any means. That’s because there are different methods that can be used to make your well water safe to drink again.

I wrote this article to give you a better idea of what coliform bacteria is, how it gets into your well water, and what steps you can take to protect your drinking water from coliform bacterial contamination.

Take it from someone like me who treated swimming pools to protect against bacterial growth for 26 years that this can be done effectively.

What Are Coliform Bacteria?


First of all, you must know that coliform bacteria are not a specific type of bacteria. They are a group that certain types of bacteria fall into. In total, 16 different species make up coliform bacteria and they all fall into one of three different subgroups. This includes:

1. Fecal coliform bacteria

These are made up of the bacteria which are always present in the digestive tracts of humans and animals.

2. Non-fecal coliform bacteria

This is coliform bacteria which can be sourced from such things as plants and surface water.

3. E. coli (Escherichia coli)

E. coli is the third and most worrisome type of coliform bacteria. It has its own sub-group because it’s considered to be the strongest indicator of potential disease-causing problems in water.

Coliform and other bacteria are also known as ‘indicator organisms’. That’s because their presence in well water does not automatically lead to illness but bacterial detection ‘indicates’ a stronger potential for illness.

Health Risks from Coliform Bacteria


Fortunately, most forms of coliform bacteria are not harmful to humans and at the most will only cause mild illness. But there are a few notable exceptions that can cause serious illness.

This includes several strains of E. coli bacteria which can build up enough in a body to produce severe toxins and even lead to death. 

Mild Forms of Illness Related to Coliform Bacterial Infections Include:

  • Cramping
  • Fatigue
  • Sudden and severe diarrhea
  • Bloating and gas
  • Fever
  • Upset stomach
  • Urinary tract infections
  • Respiratory illness

Illnesses That Result From More Severe Coliform Bacterial Infections Include:

  • Anemia
  • Pneumonia
  • Kidney failure

How Do Coliforms Get Into Well Water?

well water

When it’s found that you have coliform bacteria in your well water, it indicates that you have a contamination pathway that runs from a bacterium-producing source to your well water supply.

Here are some of the more common bacterial contamination pathways for well water:

  • Your well has been dug too shallow which allows for surface coliform bacteria to easily make their way down through the soil to your well. Flooding, runoff from heavy rains, and snowmelt are the main bacterial pathways for shallow wells.
  • There are one or more abandoned wells nearby that are contaminated and have a shared aquifer with your well
  • You or your neighbors septic system is located too close to your well
  • Improperly sealed wells
  • Defective well caps
  • Cracks or holes in well casings

How to Test for Coliform Bacteria?

safe home test

Determining if you have coliform bacteria in your well water is something that’s not too difficult to do. There are two main ways that you can go about testing your well water for the presence of coliform bacteria: 

Private Lab Testing

If you want extremely accurate bacterial test results, then having a water sample analyzed by a private testing facility is the way to go. These tests will also allow you to find out what other contaminants may be lurking in your well water too.

It must also be noted that this is typically the most expensive way to get your well water tested for bacteria.

Some will run more than $100 but that’s a fair price to pay when you consider how easy and accurate this makes detecting the presence of coliform bacteria in your well water for you.

You may be able to get your well water tested for free at a pool & spa supply store or pool chemical retail center. These stores often test water for free in the hope of getting chemical sales in return for their effort.

Mail-in test kits such as the Safe Home® Select Water Quality Test Kit are as easy to use as ordering them, filling the sample vials, and then sticking them into your mailbox for return shipping.

Well Water Test Kit

Here is the ideal method to test your well water for bacteria if you are one of those do-it-yourself-type people. DIY well water test kits usually include test strips that will detect the presence of total dissolved solids (water hardness), chlorine, lead, nitrates, and more along with having an included drop test for detecting bacteria.

The accuracy of the results of these types of tests has improved dramatically over the years so they are reliable.

These are also very simple to use. The test strips are dipped into a water sample for a few seconds and then read out against a chart on the bottle.

When testing for bacteria, you simply fill the included bottle with the proper amount of well water, shake for 20-seconds, then wait for 48-hours for a yellow (no bacteria) or green color change (bacteria detected).

I have had great success using the Verify 17 in 1 Premium Drinking Water Test Kit because it also can be used to test for the presence of bacteria in swimming pools.

Finding out if there is coliform or any other type of bacteria in your well water is something that you should emphasize. It’s so important, the many state departments of health including the New York State DOH recommend that wells be tested ‘at least’ every year for bacteria.

The Mississippi State University Extension Program recommends that you take 5 concrete steps if you do find that your well water is contaminated with coliform bacteria. These are:

  • Retest the well water to confirm the presence of bacteria
  • Do not drink the water and temporarily switch to drinking bottled water or boiling your water before drinking
  • Find the source of the problem and correct it
  • Disinfect your well
  • Retest to make sure these steps eliminated the bacterial problem

How to Get Rid of Coliform Bacteria in Well Water

So now that you know for sure that you have coliform bacteria in your well water, how do you go about getting rid of it?

That’s a great question and I will be happy to tell you about the preferred ways to do this.

These include treating your well water with chlorine, in a similar fashion to what water treatment plants do, or by placing a UV light water purification system on your incoming well water line.

Whole home well water filters are also a good option if they have an included UV filter attached.

We also curated a list of the best water filters for coliform bacteria which all contain either UV purification, chlorine treatment, or other filter media that get the job done effectively.


chemical feeder

Chlorine has been used effectively for many decades as a sanitizer and since it’s soluble it can easily be used to disinfect well water. This chemical is also very easy to measure and regulate. It’s relatively cheap so it’s great for large-scale use too.

It works as a disinfectant because chlorine is a highly reactive element. This substance is so effective at killing pathogens such as bacteria because it breaks down their chemical bonds and renders them ineffective.

To treat well water, chlorine is injected into the incoming water line using a special pump. This pump will continuously add a predetermined amount of chlorine into the incoming well water line. A control device on the system will automatically control the chlorine output that is fed into the water.

It’s a very simple and effective way to kill the coliform bacteria that is often found in well water.

UV Light Water Purification


UV light water purifiers are a great method for killing the coliform and other forms of bacteria that may be present in well water. They will also kill viruses and parasites.

How do they work?

They are not complicated devices by any means. Ultraviolet light is part of the highest end of the electromagnetic spectrum. Simply put, that means ultraviolet produces a lot of energy; enough energy to kill coliform bacteria.

UV light is produced by these coliform bacteria-killing devices using a special UV light bulb. This bulb is placed in a quartz sleeve whose job is to protect the bulb and to ensure a steady flow of UV light energy from it.

The bulb and quartz sleeve are placed inside the unit’s chamber which has two connections on it. One for allowing untreated water in the UV light purification chamber and one to let the disinfected water go on to supply your household water needs.

As the untreated water passes through the UV light chamber, any coliform bacteria that this light comes into contact with is quickly rendered ineffective.

It’s also very important to note that UV light water purifiers are not recommended to be used as stand-alone water purification devices. That’s because they do not contain a pre-filter that will eliminate water cloudiness and minerals.

The presence of which in your well water can severely impact a UV water purification system’s effectiveness. That’s why very often they are found working in tandem with water softeners or other types of well water filtration devices.

Which Filter Solution is Best for You?

I feel that UV light water purification is a much better and less time-consuming method for treating coliform bacteria in well water than chlorine injection systems are.

For one, UV light water purification systems do not impact water taste, odor, and color like chlorine treatments can. They are also low-maintenance systems too as you just set them up on your incoming well water line and pretty much forget about them.

They will continuously perform their job as long as they have power coming to them or until they need their UV light bulb changed. This usually only needs to be done every few years.

Using Chlorine injection systems to treat well water for bacteria involves constantly monitoring and adjusting the chlorine output. You will also have to make sure that the chlorine supply that feeds into the incoming well water line is kept at an adequate level.

Having to go to a supplier to purchase chlorine takes time and storing chlorine around your home can lead to even more problems.

Testing Your Well Water for Coliform Bacteria Regularly is Ultra Important

I sincerely hope that you have enjoyed reading this Coliform Bacteria in Well Water Guide and it has provided you with the important information that you need on how to detect the presence of and treat coliform bacteria in your well water.

We all know that having coliform bacteria in your well water is nothing that you want to mess around with. It can cause some very serious health issues. So be proactive when it comes to testing your well water for coliform bacteria and take steps to quickly get rid of it if it’s found.

Something else to consider is that it will never hurt you to have a chlorine injection system or UV light purification device on your incoming well water line. This is true even if you have never had a positive bacterial test result. This is especially true when you take into consideration how infrequently your well water is tested for the presence of coliform bacteria.

You can never be too proactive when it comes to minimizing the health risks that coliform bacteria in your well water pose to you and your family.

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Craig Smith
Craig got his start in water working in the swimming pool and spa industry. Water treatment would grow into his main career but he ended up working in the pool industry for over 26 years where much of his time was spent balancing the water in customer's swimming pools and installing water filtration equipment. Craig offers an abundance of water treatment knowledge after helping homeowners get pure water for 26 years.

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