How To Get Rid of Coliform in Well Water

If you rely on a private well, your water quality is your responsibility — and coliform bacteria are one of the most important issues to watch for. Found in soil, vegetation and the digestive systems of animals, coliform bacteria can enter your water supply through surface contamination, structural issues in your well—especially after recent repairs—and compromised septic systems.

While most strains of coliform bacteria aren’t harmful themselves, their presence signals that your water system may be vulnerable to more dangerous contaminants like E. coli, a fecal coliform that can cause serious illness. That’s why total coliform is used as a red flag indicator during water testing.

Whether you’re dealing with an existing problem or taking steps to prevent one, we’ll walk you through how to address coliform in well water and protect your home’s water supply.

What Is Coliform Bacteria?

Coliform bacteria are a group of microorganisms commonly found in the environment that live in soil and surface water. Their presence in a water sample typically signals that a pathway exists for contamination to enter the water supply.

Total coliform includes many types of bacteria, most of which are harmless. However, some subgroups, like fecal coliforms and E. coli, are more concerning because they specifically indicate contamination from human or animal waste.

The U.S. Environmental Protection Agency (EPA) and Health Canada both use total coliform as a general indicator of water safety. A positive result doesn’t always mean harmful bacteria are present, but it does mean your system may be compromised and should be investigated further.

How Does Coliform Get Into Well Water?

Coliform contamination in well water usually results from environmental exposure, structural damage or poor maintenance. Common sources include:

• Unsealed or cracked well caps that allow insects, dust or runoff to enter
• Damaged well casings or seals that create a direct pathway from surface water to the well
• Proximity to surface water like lakes, rivers or ponds that may carry bacteria from nearby land
• Failed septic systems or animal waste, especially after heavy rain or flooding
• Poorly maintained or abandoned wells nearby, which can act as hidden contamination channels

Because coliform bacteria are microscopic and always invisible, you may not notice a problem until you begin to see symptoms or test your water.

What Are the Health Risks of Coliform Contamination?

While total coliform bacteria aren’t typically harmful themselves, they’re a warning sign of potential bacterial contamination in your drinking water. Their presence indicates that your water system may be exposed to contaminants that pose a real risk to health — especially fecal coliform bacteria such as E. coli.

When E. coli bacteria are found in well water, the risk of illness increases significantly. According to the U.S. Centers for Disease Control and Prevention (CDC), exposure to E. coli contamination can cause:

• Stomach cramps
• Fever
• Nausea and vomiting
• Diarrhea
• Blood in urine or fecal matter

More serious E. coli infections can result in a condition called hemolytic uremic syndrome, which can lead to kidney failure or other complications — particularly for young children, older adults and people with weakened immune systems. In extreme cases, infections may require hospitalization.

Ongoing exposure to fecal coliform bacteria in your tap water or water supply increases the likelihood of waterborne disease outbreaks. That’s why testing and prompt water treatment are essential if you suspect coliform contamination.

How To Test for Coliform in Well Water

The only way to know if coliform bacteria are present in your well water is through a water test. The CDC recommends that homeowners test private wells at least once a year (and Health Canada recommends doing so every 6 months) for total coliform bacteria, as well as in the case of:

• Flooding or heavy rainfall
• Well construction or repairs
• Any signs of possible contamination

You can purchase a test kit from a certified laboratory or arrange professional water testing through a provider like Culligan. If you’re using a test kit, follow these steps to ensure a valid water sample:

1. Choose the faucet closest to the well — typically a tap at the well pressure tank or an outside faucet. 
2. Remove any aerators, sediment hoses or attachments from the faucet.
3. Sanitize the faucet with a bleach solution or flame before sampling.
4. Run the water for several minutes before collecting your sample.
5. Wash your hands thoroughly or wear sterile gloves and avoid touching the inside of the sample bottle or cap.
6. Send your sample to a certified laboratory for professional analysis.

If your results show the presence of E. coli, stop using your well water immediately and follow the guidelines set forth by the EPA and Health Canada.

How To Get Rid of Coliform From Well Water

If your well water tests positive for coliform bacteria, it’s critical to act quickly and follow a step-by-step disinfection process to protect your water supply and health. 

The following actions are supported by guidance from the EPA, Health Canada and multiple provincial and state water authorities:

1. Stop Using the Water Immediately

Until your well water is confirmed safe, stop using it for drinking, brushing teeth, cooking or washing produce. Switch to bottled water or boil water for at least one full minute. Boiling water is effective for killing harmful bacteria, but it’s a temporary solution — not a long-term fix.

If you’re on a shared or public system, notify household members or tenants and post signage where needed. Follow any boil water advisories issued by your local health department.

2. Investigate and Identify the Source

Coliform contamination can stem from multiple issues in and around your well system. Check for:

• Damaged or missing well caps
• Cracks in the casing or annular seal
• Evidence of runoff from a septic tank or animal enclosures
• Standing water near the water source
• Recent well work like pump and wire repairs or replacement

Older or shallow wells near surface water — such as lakes, ponds or rivers — are especially vulnerable. If the source of contamination isn’t obvious, consult a licensed well contractor for an inspection.

3.  Shock Chlorinate the Well

Shock chlorination is the most common way to disinfect a contaminated well. Use a chlorine solution (typically unscented household bleach or chlorine tablets) to sanitize your entire water system, including pipes, tanks and the water heater. Let the solution sit in the system for 12–24 hours without using the water.

Once the time has passed, flush the system thoroughly until the chlorine smell disappears. Be sure to follow instructions for proper shock chlorination or, to be sure it’s done correctly, hire a professional to perform the procedure safely and effectively.

4. Retest Before Resuming Use

After chlorinating your well water, it’s essential to verify that the coliform bacteria have been fully addressed. Wait a few days, then submit another water sample to a certified lab. Health authorities recommend getting two consecutive negative results, at least 24 hours apart, before using untreated water again.

More Well Water Safety Tips for Addressing Coliform

Getting rid of coliform bacteria once is important — but keeping it out for good requires an ongoing strategy. These water treatment methods can provide both short- and long-term protection:

• Boiling water is a good emergency measure, especially during floods or well repairs. It kills coliform, E. coli and other pathogens quickly.
• Continuous chlorination systems automatically inject a small, consistent dose of chlorine into your water supply to prevent bacterial regrowth.
• UV disinfection uses ultraviolet light to neutralize 99.99% of harmful bacteria and waterborne contaminants without adding chemicals to your water.
• Reverse osmosis water filtration with additional stages of filtration, like the Culligan Aquasential® Reverse Osmosis System with Advanced Post Tank Filter, offers added drinking water protection by addressing coliform, E. coli bacteria and other contaminants through a specialty filter that is certified to NSF Protocol P231 to reduce more than 99.99% of bacteria.

These tips are especially helpful if your well is located near surface water, older water infrastructure or regions prone to heavy rainfall or flooding.

Culligan’s Coliform Protection Solutions

While testing and shock chlorination can resolve many short-term problems, long-term protection takes more than a single treatment. Culligan offers a full suite of well water solutions designed to keep your water quality high and your family safe.

• Professional water testing: Accurate, certified lab testing for total coliforms, E. coli and other water contaminants
• Whole-home filtration systems: Tailored to address bacteria, sediment, hydrogen sulfide and other impurities from your water source
• Ultra-Violet Light (UV) disinfection systems: Proven to neutralize coliform bacteria contamination before it reaches your taps
• Point-of-use reverse osmosis filters: RO systems with additional filtration stages can be a powerful final barrier for drinking water safety

Every well is different, and so is every water treatment plan. Culligan’s trained specialists can help identify vulnerabilities in your water system and recommend the best combination of filtration, disinfection and maintenance for lasting protection.

Coliform contamination is a serious concern, but with the right guidance and tools, it’s completely manageable. Whether you’re addressing an existing issue or preventing one in the future, Culligan is here to help.

Schedule your free in-home consultation today.