No one wants to hear that there’s bacteria in their drinking water. A serious health concern, it’s a shock. But coliforms are more common in wells than most people realize, and thankfully easier to get rid of.
So, take a deep breath and relax. We’ll show you what to do next.
Here’s everything you need to know about coliform bacteria and how to send them packing.
What Are Coliform Bacteria?
Coliforms are a group of organisms naturally present in soil and in the digestive tract of warm-blooded animals, including human beings.
Most species are harmless but finding them in well water means disease-causing bacteria could be lurking in your cup. So-called “indicator organisms,” coliforms come from the same sources as the bacteria that can make you sick.
Among the worst is Escherichia coli (E. coli), a rare type of coliform found in animal waste that can cause serious illness, including kidney failure and death.
How Do Coliforms Get into Well Water?
An estimated 70% of privately owned wells in some areas contain coliforms. It’s not uncommon. The most common sources are leaky septic systems and agricultural runoff that seeps into ground water whenever it rains.
Properly placed well in good repair should be safe from contamination, but it’s not foolproof. Flood water can overwhelm a shallow well while a cracked casing gives microbes a way in. That’s why the CDC recommends a yearly water test for coliforms and more.
Why Test for Coliform Bacteria?
If coliforms are harmless, why test for them? Wouldn’t it be simpler to check wells for dangerous bacteria? We wish. Dozens of bacteria cause water-borne illness. It’s cost-prohibitive to test for all of them, and levels of germs like E. coli may be too low initially to detect on a water test.
But coliform bacteria multiply quickly, doubling every 30 minutes under the right conditions, so they’re easier to find. Like a canary in a coal mine, the presence of coliform in your drinking water is a warning.
What Does a Positive Test for Coliforms Mean?
Coliform water testing includes up to three parameters — total coliforms, fecal coliforms and E. coli. What do the test results mean?
The total coliform count includes all types of coliforms including those found naturally in the soil. There are 16 species in the total coliform group.
If total coliforms are high, it means other contaminants like E. Coli and parasites could be in your well.
Fecal coliform testing looks for species found in the human or animal gut. If any bacteria from the fecal coliform group is in your well, it’s been contaminated with waste.
Why is that important to know? Because sources of fecal matter are limited, making the source of contamination easier to find.
E. coli is a type of fecal coliform bacteria. Found in human and animal feces, it’s the best indicator of fecal contamination.
My Well Water Tested Positive for Coliform Bacteria! What Do I Do?
If your water tests positive for total coliform bacteria, don’t panic but take immediate action. Boil your drinking water or switch to bottled water until your well is treated.
How to Kill Coliform Bacteria in Well Water
There are five proven ways to kill coliform bacteria:
Shock chlorinating a well is similar to shocking a swimming pool. Typically a one-time treatment, the large dose of chlorine kills coliform bacteria and other harmful microorganisms.
You can do it more than once. But if repeat testing detects coliforms, it means there’s a source of bacteria near your well, your pressure tank is colonized, or your well casing is damaged. Shock chlorination is rarely a permanent solution.
A chlorine injection system is like a home water treatment plant. It adds small amounts of chlorine to the incoming water stream to kill bacteria.
Affordable, reliable, and easy to maintain, most systems require only household bleach. You can eliminate the taste by installing a carbon filter downstream.
UV Light Filtration
UV light filters kill coliforms by damaging their DNA. Unable to reproduce, they can’t make people sick.
A simple treatment system, it bombards water with UV light as it flows through the surrounding water chamber. A breeze to maintain, an annual bulb change is all it needs.
Distillers capture steam from boiling water and condense it into clean droplets. Bacteria-free, distilled water is safe to drink.
Home units start as low as $75, and they can produce up to six gallons per day of virtually pure water. More convenient than boiling, distillation is an effective way to kill coliforms and improve your overall water quality.
Preventing Coliform Contamination
The best defense against coliforms is a good offense. Here’s how you keep them out of your well.
Take Good Care of Your Septic System
A leaky septic system is a recipe for coliform contamination. Have your tank pumped and the leach bed inspected every 3-5 years.
Have Your Well Checked Regularly
Wherever a pathway exists for bacteria to enter a well, it will. Homeowners can inspect wells themselves, but small cracks in a well casing are hard to find.
We recommend calling a pro every five years or if you’ve had a positive test result for coliforms. They have the equipment and expertise needed to pinpoint the problem.
Keep Animal Waste Away from Wells
Fecal contamination runs downhill, so drill new wells higher than where your pets and farm animals defecate.
Test Your Well Water Regularly
The Environmental Protection Agency regulates total coliform levels in city water but testing a private water supply is up to you. The maximum contaminant level goal (MCLG) for public water is zero, so no amount is safe.
The CDC recommends annual well testing for several contaminants, including pH, nitrate, total coliforms and total dissolved solids. A positive nitrate test is a general indication of agricultural activity near your home. The presence of nitrate and coliforms in your well points to runoff as the source of contamination.
Install a Well Water Treatment System
Some homeowners are proactive about their drinking water quality, installing a filtration system well before they need one. If you live near a farm or in a flood plain, coliforms may not be present now, but they could be in the future. Your local health department can help you assess your risk.
See our: best well water treatment systems
Coliform Bacteria in Well Water — FAQs
Are coliform bacteria just a well water problem?
No. Naturally occurring coliforms can contaminate any surface water source — that’s why municipal water is disinfected.
Occasionally, however, a public water system may issue boil orders because samples tested positive for coliforms. We suggest keeping a case of bottled water or a biological water filter handy for emergencies.
Can I shower in water with coliforms?
Showering with coliform-contaminated water is low risk for adults but a greater concern for children. Kids should be taught to not swallow water from the tub or when brushing teeth.
Installing a KDF shower filter may remove some but not all coliforms.
Is water with coliforms safe for pets to drink?
No. Coliform bacteria is as hazardous to your pets as it is to you. Contaminated water isn’t safe for animal or human consumption.
What’s the best way to test my water for coliform bacteria?
At-home tests for bacteria are limited and less accurate than laboratory testing, so sending a water sample to a certified drinking water lab is your best bet.
Public drinking water systems are tested daily for coliforms, so problems are rare. But if you suspect an issue, it doesn’t hurt to double check. Treatment errors can occur.
For well owners, we recommend SimpleLab’s Tap Score test kits. The Essential Well Water test checks for 52 analytes and includes a nitrate, a total coliform and an e. coli test. If you drink well water, it offers complete peace of mind.
Do Reverse Osmosis Filters Kill Coliforms?
Reverse osmosis filters don’t kill coliforms, but they remove most disease-causing organisms down to 0.001 microns, including e. coli bacteria. Do they offer enough protection? Some health authorities say yes, but most say no because real-life conditions, such as how well you maintain a filter, impact their efficiency.
Most manufacturers suggest adding a UV filter or other backup method to an RO unit in case the filter fails. So do we. If you’re going to treat water with a reverse osmosis system, test it for coliform regularly and stay on top of maintenance.