How to Remove Coliform Bacteria from Well Water

It’s hard to think of anything more refreshing than a cool glass of water after an intense workout. But don’t always be too quick to take a sip. Even if the water looks clean, it could contain harmful bacteria that could make you sick. The mere thought of ingesting these nasty microbes is enough to give anyone the chills, yet millions of Americans consume them daily without realizing it.

According to the Centers for Disease Control and Prevention (CDC), over 7 million Americans fall ill yearly due to waterborne pathogens, including coliform bacteria commonly detected in private water wells. If you’re concerned about coliforms in your well water supply, keep scrolling to learn what they are, how they get into well water, common signs of their presence, and their associated health risks. We’ll also share practical advice on how to test your water for coliform bacteria and what to do to get rid of them.

What are Coliform Bacteria?

Coliform bacteria are a family of bacteria found virtually everywhere—in soil, organic matter, human and animal feces, and often well water. Super gross!

Not all coliform bacteria are created equal, though. In fact, there are three different groups, each with its own level of risk:

  • Total coliform bacteria occur naturally in the environment and are generally harmless. If they’re the only type of coliform found in your drinking water, the source of contamination is likely from soil or vegetation rather than fecal matter. But here’s the catch: if environmental pollutants can enter the water supply, there’s a chance that other more harmful pathogens could sneak in too.
  • Fecal coliform bacteria are a sub-group of total coliforms and typically live in the intestines and feces of humans and animals. If they’re detected in your well water, it’s a pretty good sign of recent fecal contamination, which means there’s a greater risk of harmful pathogens getting into your water supply and, ultimately, your drinking glass.
  • Coli bacteria are a type of fecal coliform. Most are harmless and actually play a crucial role in our gut health. However, some strains can cause serious illness. If E. coli is detected in your drinking water, it almost always means your water supply has been exposed to fecal matter.

How Do Coliform Bacteria Get into Well Water?

When it rains, the water picks up various contaminants from off the ground surface and the soil, including harmful ones like coliform bacteria. As the water flows, it transports these pollutants into surface water sources such as rivers and reservoirs and eventually into the underground aquifers that supply the water in your well.

Here are some sources of coliforms in the environment:

  • Runoff of pastures and feedlots: If animals graze near your well or it is located near a livestock facility, rainwater can wash their fecal matter containing coliform into nearby wells and contaminate the water.
  • Wild or domestic animal waste: Rainwater can also pick up and carry coliform bacteria from lands that wild and domestic animals roam and use as dumping grounds. The contaminated runoff can seep into the ground and potentially reach nearby wells, releasing coliform bacteria into the water.
  • Poorly maintained septic systems: Septic systems are designed to treat wastewater from homes and buildings. However, untreated or partially treated wastewater can seep into the ground and contaminate nearby wells when the septic systems aren’t correctly maintained.

So, how do coliform bacteria end up in well water?

  • Unscreened vents or entry points: When your well was first constructed, all entry points and vents likely had a screen placed over them to keep out creepy crawlies and critters. But as time passes, these screens can deteriorate and open your well to unwanted visitors, like coliform bacteria.
  • Unsealed well components: Now and then, Mother Nature throws us a curveball in the form of flooding. And if the seal on your well has failed, that flood water can seep right on in and contaminate your well water with all sorts of nasty bacteria.
  • A new well not disinfected: When a new well is drilled, coliform bacteria can enter the well during the drilling process, as drilling can disrupt the soil and allow bacteria to enter the well.
  • Drinking water pipes connected to non-drinking water sources: It is also possible for coliform bacteria to enter the well water system through wastewater, laundry sinks, or garden hoses. For instance, if a garden hose is connected to a water spigot also connected to the well, any bacteria or chemicals present in the garden hose can flow back into the well water—unless it has a feature to prevent this. Similarly, a cross-connection between the well water and a wastewater line could allow wastewater to enter the well water supply.

Signs of Coliform Bacteria in Well Water

While a lab test is the only way to confirm the presence of coliform bacteria in your water, there are several telltale signs that something isn’t quite right:

A foul or unusual smell

Bacteria can produce strange odors in water, such as a sulfuric, musty, earthy, or some other “off” smell. So, if something doesn’t smell right, trust your nose, as it could be a sign of coliform bacteria.

Related: Common Odors in Tap Water and How to Remove Them | How to Treat Rotten Egg Smell in Water


Is your water looking too colorful for comfort? If it has a yellow, brown, orange, or greenish tint, it could be a sign of coliform bacteria.

Cloudy water

Turbidity and sediment in the well can make the water appear murky, foggy, or hazy. If you notice these signs, there’s a higher likelihood that coliform bacteria are present.

Unusual taste

If your water has started tasting differently than usual lately, don’t ignore it because coliform bacteria can cause water to taste earthy, metallic, or even sweet.

Unexplained illness

The most obvious sign that your water may contain coliform bacteria is if you or someone in your family has become ill for no apparent reason. Coliform bacteria in water can cause stomach cramps, vomiting, and diarrhea. Don’t hesitate to get your water tested if you suspect bacterial contamination is at play.

Related: 15 Dangerous Diseases Caused by Contaminated Drinking Water

Are Coliform Bacteria in Well Water Harmful?

While most coliform bacteria won’t cause any harm, their presence could be a warning sign that other germs—including fecal coliforms—have made their way into your water source. Yup, that’s right; your water might have come into contact with poop.

Fecal coliforms are commonly found in the guts of warm-blooded animals. Some strains, like the infamous E. coli (specifically the 0157:H7 strain), can cause serious illness. If these little buggers enter your water supply, you could be in for a rough ride.

Symptoms of E. coli infection include nausea, vomiting, fever, abdominal pain, and diarrhea. These symptoms can stick around for days or even more than a week. Children and elderly folks are especially vulnerable.

In some cases, household members may have developed an immunity to common waterborne bacteria in their drinking water. That means they could drink the water without getting sick. However, visitors who haven’t developed that immunity could be in for a nasty surprise. And since the symptoms of coliform bacteria can be similar to those of other human illnesses, it can be tough to figure out what’s going on without getting your water tested.

What is an Acceptable Level of Coliform Bacteria in Well Water?

Is it safe to drink well water with coliform bacteria? Not according to the Environmental Protection Agency (EPA). They recommend a total coliform limit of zero in drinking water to ensure its safety. We suggest you regularly test the water for contaminants if you rely on a private well for your water supply. Most local environmental or health departments provide free water testing services for private wells. Alternatively, you can contact your local county extension agent for assistance. And, of course, you can also purchase a water test kit online and have your water tested by a certified laboratory.

Related: 10 Common Problems a Water Test Can Detect in Tap Water

My Well Water Has Tested Positive for Coliform Bacteria. What Now?

We understand this news can be stressful, but as mentioned earlier, coliform bacteria in well water doesn’t automatically mean you’ll get sick. Instead, there’s a chance your water contains other harmful bacteria, and you should take the following actions to address the problem:

  • Retest your water. A second test can confirm if coliform bacteria are present—and if they are, consider contacting a licensed well contractor to help you pinpoint the source of contamination and how to address it. In the meantime, avoid consuming the contaminated water. Instead, use bottled water until the issue has been resolved or boil it for at least one minute to kill harmful bacteria.
  • Maintain the well. Firstly, keep the area around the well clean and free of debris, as you don’t want any pollutants or chemicals to seep into the ground and make their way into the water source. Beyond that, test the water regularly to ensure no harmful contaminants are present. If you notice any changes in the water’s taste, color, or smell, get it tested immediately. It would be best to have your well inspected by a professional every few years to ensure it is functioning correctly and not at risk of contamination.
  • Shock Chlorination: Sometimes, a one-time or temporary event like a flood can introduce coliform bacteria into a well. Shock chlorination is used to disinfect it by adding a high chlorine concentration to the water for a short time. We recommend having shock chlorination done by a professional and retesting the water for coliform bacteria within 10 to 14 days and several months later.
  • Continuous Disinfection: If shock chlorination fails to eliminate coliform bacteria, consider investing in a chemical injection system. These systems inject a chlorine solution or dry powder into the water ahead of a storage tank to disinfect the water continuously.
  • Install a UV Water Purification System. UV water systems emit ultraviolet light that penetrates the cell walls of the bacteria, disrupting their DNA and preventing them from replicating. As a result, the bacteria are effectively sterilized and cannot cause harm. However, UV systems are ineffective against contaminants like chemicals and heavy metals. That’s why we recommend installing a whole-house well water filter system to eliminate non-bacterial pollutants and then adding the UV water purification system to destroy all pathogens.

Is Boiling Effective Against Coliform Bacteria?

Boil Water For Distillation
Boiling Water For Distillation

Boiling the water for about a minute can effectively kill any bacteria lurking in it. It’s a tried-and-true method often relied upon during emergencies or outdoor excursions. But please bear in mind that boiling can be pretty demanding in terms of time and energy, and you’ll only be able to boil small amounts of water at a time. So, while boiling is an excellent short-term solution, it’s not a sustainable or scalable way to disinfect your water consistently.

Final Thoughts

We all want to be confident that our drinking is clean and safe. But unfortunately, contaminants like coliform bacteria often go undetected in private wells and may endanger our health. By being aware of the potential sources of coliforms, performing regular water tests, and taking steps to remove them, you can safeguard your water supply and protect your loved ones from the risks of waterborne illness. Prevention is always better than cure, so stay safe, vigilant, and informed.

If you want to learn more about our whole-house well water filter system, chemical injection system, or UV Purification system, contact us at 800-589-5592 or via chat.