Bacteria in Well Water (Everything You Need to Know in 2024)

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Bacteria is one of the most dangerous drinking water contaminants. The good news is that you can protect your well system from bacterial pathogens, so owning a private well doesn’t have to mean putting yourself at risk of waterborne disease.

Here, we’ve shared everything you need to know about coliform bacteria in a well supply, including what it is, how it gets there, its health effects, how to protect your well, and more.

📌 Key Takeaways:

  • Bacteria are harmful pathogens that may enter a well system as a result of surface water runoff, flooding, and groundwater movement.
  • You may experience diarrhea, vomiting, nausea, and stomach cramps as a result of ingesting drinking water that contains bacteria.
  • The US Environmental Protection Agency (EPA) recommends testing water at least once a year for total and fecal coliform bacteria.

❔ What Are Bacteria in Well Water?

Bacterial contamination in well water is when a well supply becomes contaminated with bacteria, a type of disease-causing microorganism.

By law, all municipal water supplies for drinking in the US have to be microbiologically safe, meaning that they’re treated (usually with disinfection treatment) to kill or remove these pathogens before water is delivered to our homes.

However, private well water systems aren’t regulated by the US Environmental Protection Agency (EPA). That doesn’t mean that they’re unlikely to be contaminated with bacteria – it simply means that the well owner must take responsibility to test for, and remove, microorganisms if they’re detected.

Bacteria in your water suggests that your well has become contaminated with human or animal waste, which may have also introduced other microorganisms, like protozoa and viruses, into your water supply.

well water bacteria contamination

Total Coliforms Vs Fecal Coliforms

Total coliform bacteria are found in soils, waters, and human and animal waste. These bacteria aren’t harmful, but their presence often indicates that other bacteria with health effects are present.

Fecal coliform bacteria are a type of bacteria that are specifically found in the guts of warm-blooded animals. Their presence tells you that your well water has been contaminated by human and animal waste, and may make you sick.

🚰 How Do Bacteria Get Into Well Water?

Bacteria get into well water due to surface runoff or seepage from nearby contaminated areas.

Some of the likely sources of bacteria are:

  • Leaking or overflowing septic systems
  • Animal feedlots
  • Nearby rivers, lakes, or other surface water sources
  • Farmland
  • Sewers

There are a few conditions that may increase the likelihood of bacterial contamination in a private well. These include:

  • Damaged or cracked well casing
  • Poor well structure
  • Recent work carried out on the well and water system
  • Flooding
  • Well positioned too close to sources of contamination
  • Old wells constructed prior to the introduction of state regulations

Ultimately, if your well is new and sturdily constructed, and there’s no damage to your well casing or other components, you’re at a much lower risk of bacterial contamination.

Concrete well cap not sealed properly

🩺 Health Effects Of Bacteria In Well Water

The exact health effects of bacteria in private wells depend on the type of bacteria found.

Most bacteria don’t cause long-term health problems. However, some types of bacteria may cause various diseases, with short-term symptoms including:

  • Diarrhea
  • Abdominal cramping
  • Nausea
  • Fever
  • Headaches
  • Dizziness
  • Lethargy

The symptoms you experience, and how long the symptoms last, depend on which bacteria you ingest. Most waterborne bacterial diseases last for up to 2 weeks.

The good news is that most coliform bacteria aren’t harmful and won’t have any health effects. However, the presence of one type of coliform bacteria indicates that other bacteria, such as E. coli (which will make you sick), are also present, suggesting a problem with your well structure.

Feeling sick after drinking well water contaminated with bacteria

👩🏽‍⚕️ How To Protect a Well Supply from Bacteria

There are a few things you can do to protect your well water from bacterial contamination:

Inspect Your Well Regularly

Your first responsibility is to inspect your well regularly.

Your well structure will degrade naturally over time, and severe weather or natural disasters – such as flooding, hurricanes, and earthquakes – may damage your well or cause it to become contaminated by pathogens from the surrounding environment.

There are a few things to look out for on a well inspection:

  • Damage: Examine the well for holes and cracks in the casing, loose wires, and corrosion.
  • Connections: Check that the electrical conduit and other connections are still watertight.
  • Well cap: Ensure the well cap has a secure seal and has no broken parts or cracks.
  • Nearby debris: Remove any debris positioned near the well.
  • Isolation distances: Any possible contamination sources (such as pesticides, septic systems, fertilizers, and feedlots) should be a suitable distance from the well – typically at least 50 feet.

Visually inspect your well once in every season of the year, or whenever the well’s structure may have been compromised. Hire a professional well contractor to conduct an annual inspection for mechanical and structural issues.

Test Your Water Every 1-2 Years

Alongside inspecting your well, you should also test it for bacteria every 1-2 years.

Even if you don’t think your well contains bacteria, it’s still important to test your water to check that nothing has changed, since wells can become randomly contaminated by microorganisms without warning.

Choose an accredited laboratory to test your water. The process is simple: take a sample of your tap water, then send it to the laboratory and await your test results.

Water testing with tap score

Our tip: We recommend testing for total coliform bacteria, which is known as an indicator bacteria because its presence indicates that other harmful pathogens are also present in a drinking water supply.

There are a few occasions when you should switch to bottled water (boiling water is also fine) and test your well as soon as possible:

  • If your well is in poor condition, according to a recent inspection
  • If your well is in the vicinity of a leaking or malfunctioning septic system
  • If floodwater has contaminated the well
  • If you have abandoned wells or feed yards on your property
  • If your family members or visitors are experiencing gastrointestinal issues that can’t be linked to other events
  • If your well has a history of bacterial contamination
Taking a water sample from faucet for testing purposes

Shock Chlorinate Your Well

The best way to react to suspected coliform bacteria contamination is to shock chlorinate your well.

You can use a liquid chlorine solution or dry pellets for shock chlorination. Remove the well cap and add the chlorine bleach directly to the well.

You’ll need to flush the water through your plumbing system after letting the chlorine solution sit for at least 6 hours (ideally overnight). This will remove the hazardous chemicals and make your drinking water safe to ingest.

Two weeks after the chlorine odor is no longer detectable in your water, do another water test for bacteria to confirm that it has been effectively removed from your well system.

Shock chlorination treatment should kill fecal coliform bacteria and any other microorganisms that have contaminated your well system.

👨‍🔧 We’ve shared the step-by-step for shock-chlorinating private wells in our well water shock chlorination guide.

If shock chlorination doesn’t work, hire a professional well contractor and discuss the issue. You might need to replace a section of your well or even construct a new well.

Install A Water Treatment System If Necessary

Finally, if your water tests positive for bacteria or you want to protect your family against microorganisms without the potential of getting sick, we recommend installing a water treatment system that will remove or kill bacterial contaminants.

There are a few different treatment methods for private water systems. We recommend checking out ultraviolet (UV) purifiers, which expose water to UV light.

UV treatment can kill bacteria and other microorganisms by scrambling their DNA, preventing them from replicating.

You can install a whole-home UV system to eradicate microorganisms from your well water supply before it travels through your home’s pipes and plumbing. Just make sure your water is clear (non-turbid), or the UV treatment won’t work effectively. Install a pre-treatment filter, like a sediment or tannins filter, if necessary.

Whole house water filter and sediment filter next to uv water purifier

🦠 A Word on Iron Bacteria

If your well water is contaminated with iron (or manganese) and bacteria, you might have iron bacteria.

These bacteria are a combination of iron or manganese and oxygen, which form bacterial cells, rust, and a brownish-orange, slimy substance that clogs your well components and plumbing system. They may live in your groundwater or they may enter a new well through the use of contaminated materials for the well construction.

Iron bacteria aren’t usually dangerous, but they’ll give your water a foul taste and have damaging effects in your well, plumbing, fixtures, and appliances.

Disinfection with chlorine is the best way to kill iron bacteria, but this method of water treatment isn’t guaranteed to be 100% effective because the bacteria may bind with, and inactivate, the chlorine.

We recommend contacting a professional well contractor in your area to discuss the best way to tackle iron bacteria in your well.

⚠️ Other Possible Well Contaminants

Aside from total coliform bacteria, there are other contaminants that might compromise your well water quality.

These include:

  • Nitrates and nitrites – Test for these every other year.
  • Lead – Test for this toxic metal at least once (to determine your well and household plumbing system don’t use lead materials).
  • Arsenic – Test for this contaminant at least once. Arsenic is naturally present in the earth’s crust and can have dangerous health effects.
  • Manganese – Test for this contaminant at least once if you have babies or young children who drink water from your well.
  • Hydrogen sulfide – Test for this contaminant at least once or when your water develops a rotten egg odor.
  • Fluoride – Test for this mineral if young members of your family drink well water.
  • Volatile chemicals – Test for these at least once if you live near an industrial or commercial area.
  • Pesticides and herbicides – Test for these regularly if you live in an agricultural area.

📝 Final Word

Bacteria will compromise your water quality and might make you sick.

If you own a private well, get your water tested at least once a year for this pathogen, or more frequently if necessary.

Shock chlorination should kill bacteria in your water, but you might want to install a permanent solution for killing microorganisms, such as a UV light bulb, for peace of mind.

  • Brian Campbell
    President & CEO, CWS, CWR

    Brian Campbell, a WQA Certified Water Specialist (CWS) and Certified Water Treatment Representative (CWR) with 5+ years of experience, helps homeowners navigate the world of water treatment. After honing his skills at Hach Company, he founded his business to empower homeowners with the knowledge and tools to achieve safe, healthy water. Brian's tested countless devices, from simple pitchers to complex systems, helping his readers find the perfect fit for their unique needs.

4 thoughts on “Bacteria in Well Water (Everything You Need to Know in 2024)”

  1. Avatar for Brian Campbell

    Hi. I’m a new widow & of course everything that could go wrong has this 1st year.
    My well is probably 30yrs old. Never had this problem this bad before. The filters have all of a sudden filled with that brown/ rust color you spoke if in your article. My husband had a all house purifier put in right before he died. For about 8 months, the filters have been completely covered in this mess! The all house water filter system has the same problem. The water taste fine, so far. I’m taking the water to be tested on Monday, as they were closed today & tomorrow. My well guy says he can put something called “seriline, or Seratine, something that sounded like that??…& let it sit for 24hrs. We cannot use any water for that period. $450.00. Is this correct to have done to rectify my problem? No iron deposits showing up in sinks/showers, yet. Before having our all house system put in, we did have “rust spots” buildup issues. Hope you can help me!! Thank you for what you do for everyone online!
    Pat A

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