Coliform Bacteria in Well Water: Problems, Testing and Removal

One of the most important things in maintaining well water quality is to ensure that it is free from bacteria and other disease-causing microorganisms. Bacteria are the most contaminants in well water. Among the bacteria family, coliform bacteria are found in the majority of the wells in the U.S. In this article, we are going to discuss.

  • How coliform bacteria enter the water
  • What diseases they can cause
  • When and how to test your water and interpretation of the test results
  • How you can remove them from your water
  • What preventions you can take to stop the re-entry of bacteria

Before we begin, let’s read some basics about coliform bacteria.

What are coliform bacteria?

Coliform bacteria are a common species of bacteria. They are mostly found in soil, surface water, plants, and the intestines of human beings and warm-blooded animals. A majority of bacteria from the coliform family are harmless, but a few can cause mild to severe diseases. Coliform bacteria in well water are referred to as indicator organisms because their presence in drinking water is an alarm for the disease-causing bacteria in water.

How Coliform Bacteria enter the Well Water?

Coliform bacteria can enter the well water through the following ways.

  • They are washed into the ground by rainwater, melting snow, irrigation channels.
  • From woodlands, pastures, or animal feedlots.
  • From animal waste.
  • Poorly maintained septic system.
  • Damaged well cap and well casing.
  • Unplugged or improperly decommissioned abandoned well nearby.
  • Wells located in close proximity to the septic system and sewage pipes are at high risk of bacterial contamination. Check your state laws for well site selection.
  • Connecting drinking water pipes to non-drinking sources such as wastewater, laundry, and dishwashers.
  • Wells can get polluted due to the use of contaminated drilling tools, casing pipes, or drillers. Well construction in poor sanitary conditions may also be the reason behind well contamination.
  • The aquifer is highly fractured, and bedrock and the gravel deposit do not provide an effective filtration to remove bacteria.

What Diseases can Coliform Bacteria cause?

When coliform bacteria are present in water, it does not mean that you will be catching diseases from them. Rather, it is an indication that a pathway is open, which can lead to contamination from disease-causing bacteria. Common health issues related to coliform bacteria are:

  • Vomiting
  • Fever
  • Diarrhea
  • Nausea and upset stomach
  • Hepatitis
  • Cramps
  • Headaches
  • Fever
  • Body fatigue and lethargy

If you find E.coli in your well water, you are at a higher risk. In such cases, you need to take swift action as it can cause severe health issues, and continued exposure can even lead to death. E.coli bacteria are also known as fecal bacteria. They are specific to the fecal wastes of human beings and animals. Its presence indicates a more serious problem at hand; your well is being polluted by an animal or human waste. The sewage waste is entering the well, and it needs to be stopped. Infants, children, older people, and people with weak immunity and self-defense are at a greater risk than normal healthy individuals.

Testing for Coliform Bacteria

The EPA and all the states strongly recommend that all private drinking water sources be tested annually for coliform bacteria. You must get your well water tested if:

  • You notice a change in the taste, smell, and color of the water.
  • The water appears cloudy after it rains, or the wellhead is flooded.
  • If your family experiences an upset stomach, vomiting, fever, diarrhea, or any of the above symptoms and they won’t go away after taking medicines.
  • Your well is located within 50 feet of a contamination source like a sewage pipe or septic tank.

How to Test?

testing coliform in laboratory

You can either test your water at home or hire the service of a certified testing facility. We suggest that you contact a state-approved testing facility for getting your water tested. They may charge you a little more, but their results will be authentic compared to a home testing kit. You can contact your local health office to get a list of the licensed labs in your area.

Coliform Bacteria Treatment

Treating coliform bacteria from well water needs you to work on two fronts.

  1. Removal
  2. Prevention


Drink Bottled Water – When you find that there are coliform bacteria in your well water, stop drinking water from your well unless you eliminate the bacteria in it. The best way to avoid this is to start drinking bottled water for a short time. Make sure you don’t use contaminated water for drinking and cooking purposes.

Chlorination of well water

Shock Chlorination – Using chlorine to remove bacteria from well water is one of the most trusted and reliable methods. City water authorities periodically chlorinate water to remove microorganisms. Shock chlorination refers to one-time chlorination and is mostly carried out after a heavy rainstorm flooding or well repair, modification, or when a new well is built. A high chlorine concentration is added to your water, and then the water is tested again after 12-14 days to confirm that bacteria are no longer found in your water.

Continuous Chlorination – For some wells, shock chlorination may not work. If this is the case with your well, you need to chlorinate your water regularly. Continuous chlorination techniques are used worldwide to disinfect water. Continuous chlorination is done with an injector. The injector is installed after the water leaves the well. The amount of water passing from the injector automatically takes the amount of chlorine needed for disinfection. For better results, a sediment filter must be installed before a chlorinator. Continuous chlorinator machines need regular maintenance. You will need to refill the chlorine periodically as it is consumed while removing bacteria and when other contaminants come in contact with chlorine.

UV Light for well water purification

UV Light – Another way to remove bacteria from drinking water is to use UV light. You may use UV light separately or as part of another filter. With UV light, the maintenance needs are very less. You just have to replace the UV bulb after 12-18 months. However, UV light is not recommended when the coliform bacteria colonies exceed 1,000 colonies per 100 mL, or fecal bacteria have more than 100 colonies in 100 mL. When water moves over the glass sleeve, the UV radiation kills the bacteria. In order to get the best results, the incoming water must be free from sediments, turbidity, and other contaminants. The only disadvantage of using a UV light bulb is that it will not deal with the bacteria introduced after the water leaves the UV Purification chamber. The best way to deal with this problem is to install a UV light filter with an under sink RO filtration plant. It provides pure water for drinking and cooking. A reverse osmosis filtration unit is best when dealing with a variety of contaminants in water.

Boiling – For small amounts of water or emergency and outdoor trips, boiling the water for at least 1 minute will give you bacteria-free water. You must make sure to boil the water for 1-2 minutes when the water is bubbling in the pot. Boiling is a time-consuming and energy-intensive technique and will only produce bacteria-free water in a very less amount.

Iodination – Iodination is recommended by EPA as a short-term or emergency measure to kill bacteria in water. Long term use of iodine is not healthy and can lead to severe side effects from iodine exposure. A lot of campers and hikers use iodine tablets to disinfect drinking water. Iodine adds a particular taste and smell of drinking water.

Ozone – Ozone is a strong oxidant with the potential to kill bacteria and other microorganisms. Ozone is injected into the water with the help of an ozonation injector. Ozone treatment units are very costly as compared to chlorinators and UV light chambers.

Re-testing your Water

Once you decide to adopt a removal method, you must get your water tested again to confirm that the chosen remedy is working all right. If the test results still show bacteria in water, you must contact a certified driller and decide the future course of action.


We all have heard that prevention is better than cure. It is also cheaper than installing costly treatment units. If you are diligent while selecting the drilling place and do it according to your local state laws, use approved materials, and hire licensed contractors; there is a high chance that you will not suffer from bacterial contamination in water. However, bacteria can still find their way into your well. Following prevention techniques will help you keep bacteria away from your drinking water.

  • Regular well inspection for damages to well cap and well casing.
  • Look for corrosion in well pipes, loose wires, or soil settling.
  • Keep the well area clear of debris.
  • Install concrete pads on the side of the well cap.
  • Do not keep possible contamination sources such as fertilizers, pesticides, septic tanks, and feedlots near your well. Maintain at least 50 feet safe distance.
  • Old wells, wells with leaked caps and casing, and wells too close to a septic system, sewage lines, and animal feedlots are more susceptible to bacterial contamination.

Final Words

One should never ignore annual water testing for well water. The hassle and cost of a water test are far less than the suffering from diseases. A water test allows you to make sure that no contaminants are present in your drinking water and helps you install the right treatment unit.

Leave a Comment