What to Do if Your Well Water Test Comes Back Positive?

If your well water test comes back positive, stop using the water for drinking, cooking, and brushing teeth right away. Switch to bottled water or boil tap water at a rolling boil for one minute before any use. Then shock chlorinate the well to kill the bacteria, find and fix the source of contamination, and retest at a certified lab to confirm the water is safe before going back to normal use. According to the U.S. Environmental Protection Agency, the goal for total coliforms and E. coli in drinking water is zero, so even one positive result means action is needed. This article walks through exactly what each step looks like, how serious different types of contamination are, what symptoms to watch for, and when to call in professional help.

What Does a Positive Well Water Test Result Mean?

A positive well water test result means that bacteria, nitrates, or another contaminant has been detected in your water at a level that does not meet safe drinking guidelines. According to the U.S. Geological Survey, more than 43 million people in the United States rely on private wells, and a USGS study of 2,100 private wells found that about 1 in 5 wells contained one or more contaminants above a human-health benchmark. The EPA goal for both total coliforms and E. coli in drinking water is zero, so a single positive coliform result for a private well means the water should be considered unsafe to drink until the issue is fixed.

Most positive results fall into two main categories: bacterial contamination like total coliform or E. coli, or chemical contamination like nitrates or heavy metals. Bacterial issues are the most common and the most urgent because they can cause illness within days. Chemical issues are often slower in effect but can be just as serious over time. According to a Penn State Extension study of 450 private wells, about 35% contained coliform bacteria, which shows just how common this kind of positive result is. Across Mid-Missouri, where many homes outside Cuba, Rolla, and Jefferson City rely on private wells, annual testing is the best way to catch problems early.

What to Do if Your Well Tests Positive for Coliform?

If your well tests positive for coliform, stop drinking the water, use bottled or boiled water for all consumption, shock chlorinate the well, inspect the well system for entry points, and retest to confirm the water is clean. The EPA recommends rolling boil for at least 1 minute (3 minutes if you live above 6,500 feet elevation) to kill bacteria, viruses, and parasites in the meantime. According to the CDC, a positive total coliform test is a warning sign that disease-causing germs may have a pathway into your well.

The full action plan looks like this. First, stop using the water for drinking, cooking, making ice, brushing teeth, or washing fresh produce. Second, switch to bottled water for all of those uses until the well is cleared. Third, inspect the well cap, casing, and the area around the wellhead for cracks, gaps, or signs of recent disturbance. Fourth, shock chlorinate the well using unscented household bleach, which the EPA and most state health departments recommend as the standard first response. Fifth, wait at least 72 hours after the chlorine has cleared from the system before retesting. Sixth, send a fresh sample to a certified lab for a follow-up well water testing round to confirm the issue is resolved.

How Serious Is Coliform in Well Water?

Coliform in well water is serious because it indicates that surface contamination has a way into your drinking water, even if the coliform itself is not always harmful. Most coliform bacteria live in soil, plants, and animal digestive tracts and will not make a healthy person sick on their own. The problem is that coliform gets into water the same way as harmful germs like E. coli, Salmonella, and norovirus do. According to the EPA Revised Total Coliform Rule, public water systems must keep coliform detections under 5% of monthly samples, but for a private well a single positive result is considered unsatisfactory for drinking.

The seriousness depends on which type of coliform shows up. Total coliform is a broad warning flag. Fecal coliform points to direct contact with human or animal waste. E. coli is the most urgent because its presence almost always means fresh fecal contamination and a real disease risk. Homeowners in rural Missouri often have wells near agricultural fields, livestock, or older septic systems, all of which raise the risk of coliform showing up after heavy rain or spring runoff.

What Is Worse, E. coli or Coliform?

E. coli is worse than total coliform because E. coli almost always means fresh fecal contamination and a direct disease risk, while total coliform is a broader warning that something has gotten into the well. E. coli is one specific bacterium in the fecal coliform group. According to the CDC, a positive test for E. coli or fecal coliform likely means that feces have gotten into your well water, along with any harmful germs that come with it.

The health gap between the two is large. Most strains of common coliform bacteria do not cause illness in healthy people. E. coli, on the other hand, can cause severe gastrointestinal illness, kidney failure in young children and elderly adults, and in rare cases death. According to the World Health Organization, the incubation period for E. coli O157:H7 ranges from 3 to 8 days, with a median of 3 to 4 days. Approximately 10% of children infected with E. coli O157:H7 develop hemolytic uremic syndrome, a serious kidney complication. Any well that tests positive for E. coli needs immediate action, not just a wait-and-see approach.

Can I Still Drink My Well Water with Coliform?

No, you should not drink your well water with coliform present until the contamination is treated and the water retests clean. Even though most coliform bacteria are harmless on their own, their presence shows that something is getting into your well, and the same pathway can let harmful germs in. The EPA’s health-based goal for coliform in drinking water is zero, which means there is no safe level for routine consumption from a private well.

Until the well is cleared, you have three short-term options. You can drink bottled water, which is the simplest and most reliable choice. You can boil tap water at a rolling boil for one full minute, which kills bacteria, viruses, and parasites but does not remove chemical contaminants. Or you can use a certified filter with an absolute pore size of 0.3 microns or smaller, which the CDC notes can remove most bacterial contaminants. Boiling and bottled water remain the safest choices for infants, pregnant women, elderly adults, and anyone with a weakened immune system.

Is It Safe to Shower with Water That Has Coliform Bacteria?

It is generally safe to shower with water that has coliform bacteria as long as you do not swallow any water and you avoid getting it in your eyes, nose, or any open cuts. Healthy adults face very low risk from short, careful showers. The CDC and most state health departments note that the main route of infection from coliform is ingestion, not skin contact, so a regular shower with mouth closed is usually fine for the short term.

Children, infants, and people with weakened immune systems should avoid showering and bathing in coliform-positive water until the problem is fixed. Young children are more likely to swallow water during a bath, and people with compromised immune systems face higher risk from even small exposures. If E. coli is also present in the test result, the safer option is to use bottled or boiled water for sponge baths until the well is cleared and retested. Keep showers short, use lukewarm water rather than hot to limit aerosol exposure, and do not brush teeth in the shower.

Can You Wash Dishes in Water with Coliform Bacteria?

You can wash dishes in water with coliform bacteria if you take extra steps to disinfect the dishes afterward. Run the dishwasher on its hottest setting with a heated dry cycle, which reaches temperatures high enough to kill most bacteria. If you hand wash, add one teaspoon of unscented liquid bleach per gallon of rinse water and let dishes air dry. The CDC and EPA both note that water hot enough for a normal dishwasher heated dry cycle, typically 150 degrees Fahrenheit or higher, kills coliform and most other waterborne pathogens.

For baby bottles, sippy cups, and any utensil that goes in a young child’s mouth, do not use coliform-positive water at all. Wash these items with bottled water or boiled-and-cooled water until the well retests clean. The same goes for any cooking that does not involve heat, like making salads, washing fresh fruit, or mixing baby formula. Heat is your friend for dish disinfection. Cold rinses are not.

What Are the Symptoms of Contaminated Well Water?

The symptoms of contaminated well water include stomach cramps, diarrhea, nausea, vomiting, fever, headache, and fatigue. Some people also notice that their water has a musty, earthy, or rotten egg smell, but many contaminated wells produce water that looks, tastes, and smells normal. According to the EPA, fecal coliform and E. coli are bacteria whose presence indicates the water may be contaminated with human or animal wastes, and the disease-causing microbes in those wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms.

Less obvious signs include unexplained illness in multiple household members at the same time, repeated stomach problems in children that improve when they are away from home, and rashes or skin irritation after showering. According to U.S. Geological Survey research, health risks tied to contaminants in domestic well water include gastrointestinal illness from bacteria and pathogens, plus longer-term exposure risks from nitrates, arsenic, radon, lead, and organic compounds. The Conversation reports that at best, only half of private well owners test their water with any regularity, which means many illnesses tied to well water never get linked back to the source. A buyer’s inspection with water testing helps spot these issues before they become health problems.

How Quickly Will You Get Sick from Contaminated Water?

You can get sick from contaminated water within hours to several days depending on which bacteria, virus, or parasite is present. Norovirus and Shigella can cause symptoms within 12 to 48 hours. Salmonella typically takes 6 to 72 hours. E. coli O157:H7 has an incubation period of 1 to 10 days, with most cases showing symptoms in 3 to 4 days, according to both the World Health Organization and the CDC.

The amount of bacteria matters too. A small dose of E. coli might cause mild symptoms or none at all in a healthy adult, while the same dose could put a young child in the hospital. According to CDC reports on E. coli outbreaks, illness usually resolves in 5 to 10 days for most people, though about 5% to 10% of E. coli O157:H7 cases develop hemolytic uremic syndrome, which can cause kidney failure. If anyone in the household develops gastrointestinal symptoms within a few days of using positive well water, contact a doctor and mention the positive water test result so the right tests can be ordered.

What to Do When a Well Test Comes Back Positive for E. coli?

When a well test comes back positive for E. coli, treat it as an emergency. Stop using the water for any purpose that involves ingestion, including drinking, cooking, ice making, washing produce, and brushing teeth. Switch to bottled water immediately, even for pets. Contact your local health department to report the result, since many counties offer guidance and follow-up testing for E. coli cases. Shock chlorinate the well and have the entire well system inspected by a licensed professional before retesting.

Because E. coli almost always points to direct fecal contamination, the source is usually nearby. Look for a failing septic system, a damaged well cap, surface water running toward the wellhead, livestock or wildlife waste near the well, or recent flooding. Wells with damaged casings, casings that end too close to ground level, or shallow bedrock fractures need professional repair before chlorination will hold. A regular inspection of the septic system can rule out one of the most common sources of E. coli contamination in rural homes throughout Mid-Missouri. Pair the cleanup with a follow-up water quality test from a certified lab to confirm the well is fully clear before drinking from it again.

How to Get Coliform Out of a Well?

You get coliform out of a well by finding and fixing the source of contamination, shock chlorinating the entire system, flushing the chlorine out, and retesting to confirm the bacteria are gone. Skipping any one of these steps usually means the coliform comes back within weeks. According to the EPA and most state extension services, shock chlorination is the standard first-response treatment recommended for any positive coliform result.

The full process starts with an inspection. Walk the area within 100 feet of the wellhead and look for failing septic lines, animal waste, lawn chemical runoff, low spots where rainwater pools, or any direct path from the surface into the well. Check the well cap to make sure it is sealed tight and not cracked. Confirm that the well casing extends at least 12 inches above ground. Look at the area around the wellhead for any cracks or settling. Once any obvious problems are fixed, shock chlorinate the system. If the well keeps testing positive after multiple rounds of shock chlorination, a permanent treatment system like a UV light or a continuous chlorination unit may be needed. Issues like these often show up during a full home inspection when the inspector pairs well testing with a property walk-through.

Will Shocking a Well Get Rid of Coliform?

Shocking a well will get rid of coliform in many cases, but not always permanently if the source of contamination is still there. A Penn State Extension study of wells contaminated with coliform bacteria found that shock chlorination paired with installation of a sanitary well cap successfully removed the bacteria for one year in about 15% of treated wells. The success rate was much higher for wells with low colony counts (under 10 colonies per 100 mL) and no E. coli present at all.

Shock chlorination works as a one-time disinfection event. It kills bacteria living in the well casing, the pump, the pressure tank, and the household plumbing at the time of treatment. It does not prevent new bacteria from entering the well later. If contamination keeps coming back after multiple shock treatments, the well most likely has a structural problem like a broken casing or a damaged seal, or there is an ongoing source like a leaky septic line or surface runoff that needs to be addressed at the root.

Can I Chlorinate My Well Myself?

You can chlorinate your well yourself in many cases, though hiring a licensed well professional is the safer choice for complex systems or repeat contamination. The basic process involves calculating the right amount of unscented household bleach for your well’s diameter and water depth, pouring it into the well, circulating it through all faucets and fixtures, letting it sit for at least 12 to 24 hours, and then flushing the system until the chlorine is fully cleared. According to Maine state health guidelines, chlorine is roughly 100% effective as a disinfectant at a water pH of 5.5 but only 34% effective at a pH of 7.6, which is why testing pH first matters.

Safety steps matter. Never mix bleach with any other cleaner. Open windows and ventilate any enclosed space near the well. Wear gloves and eye protection. Do not use scented or splashless bleach since the added chemicals can damage your pump and pipes. Do not drink, cook with, or bathe in the water during the chlorination period. After flushing, wait at least 72 hours before collecting the retest sample to make sure the chlorine has fully cleared. If the retest comes back positive again, do not chlorinate a second time without first having the well system professionally inspected for damage or design problems.

Why Does My Well Keep Testing Positive for Coliform?

Your well keeps testing positive for coliform because there is an ongoing pathway for contamination that shock chlorination cannot fix on its own. The most common reasons are a cracked or missing well cap, a damaged well casing, a casing that ends too close to ground level, a nearby failing septic system, surface water running toward the wellhead, and shallow bedrock fractures that let groundwater carry bacteria in. According to Maine and Virginia state extension materials, if any of these structural issues exist, no amount of shock chlorination will permanently solve the problem.

Less obvious causes include a biofilm buildup inside the well or plumbing that protects bacteria from chlorine, a deep well that draws from a contaminated aquifer, or a household water softener or filter that has been harboring bacteria. Wells located downhill from animal feeding areas, septic drain fields, or agricultural fields face higher ongoing risk. If your well has tested positive more than twice in a year, the next step is a full system inspection by a licensed well contractor, not another round of bleach. A long-term solution like a UV disinfection system or continuous chlorination may be required. Issues with common home inspection findings often overlap with the same conditions that lead to repeat coliform problems.

Coliform vs E. coli Comparison Table

The table below shows how total coliform and E. coli compare on key health and action points. Use it as a quick reference if your lab report shows one or both.

Sources: U.S. Environmental Protection Agency, Centers for Disease Control and Prevention, World Health Organization, U.S. Geological Survey, Penn State Extension, Maine Department of Health and Human Services.

Frequently Asked Questions

Is It Common to Have E. coli and Coliform in Well Water?

It is common to have coliform in well water, and less common but far from rare to have E. coli. A Penn State Extension survey of 450 private wells found that about 35% contained coliform bacteria. The American Society of Microbiology and state health agencies estimate that anywhere from 5% to 20% of private wells in different regions also test positive for E. coli at some point. Wells located near livestock, septic systems, or agricultural fields face the highest risk.

Is It Okay to Drink Water with Coliform?

It is not okay to drink water with coliform present in a private well, because the EPA’s health-based goal is zero coliform in drinking water. Even though many coliform strains are harmless, their presence means that disease-causing germs may also be in the water. Switch to bottled or boiled water until the well is cleared and a follow-up test confirms the water is safe.

How Often Should I Test My Well Water?

You should test your well water at least once a year for total coliform, nitrates, total dissolved solids, and pH, according to the CDC. The EPA also recommends additional testing after any flooding, nearby construction, well repair, or sudden change in taste, color, or smell. Reports from the U.S. Geological Survey show that at best half of private well owners test with any frequency, and very few test once a year as recommended, which is why so many problems go undetected.

Can Boiling Make Well Water Safe to Drink?

Boiling can make well water safe to drink if the contamination is bacterial, viral, or parasitic, but it cannot remove chemical contaminants like nitrates, arsenic, lead, or pesticides. The CDC recommends bringing water to a rolling boil for one full minute at low elevations and three minutes at elevations above 6,500 feet. Boiling is a short-term fix while the well is being chlorinated and retested, not a long-term solution.

Does Heavy Rain Affect Well Water Quality?

Heavy rain affects well water quality by washing surface contaminants like fertilizer, manure, septic overflow, and dirt into wells, especially older shallow wells or wells with damaged casings. Many wells that test clean year-round will suddenly test positive for coliform after a major storm. The EPA recommends testing any private well within a week or two of a flood event, hurricane, or extended period of heavy rain, even if the water looks normal.

Should I Test Well Water Before Buying a Home?

You should test well water before buying a home if the property is on a private well, especially in rural areas or near agricultural land. According to USGS research, about 1 in 5 private wells contain at least one contaminant above health-based standards, and standard real estate inspections do not always include water sampling. Buyers can pair water testing with a pre-listing inspection or a buyer’s inspection to get the full picture of the property’s water and structural condition before closing.

Can a Home Inspector Test My Well Water?

A home inspector can collect well water samples and send them to a certified laboratory for analysis as part of a property inspection. Most standard home inspections do not include water testing automatically, so it is usually added as a separate service. We provide certified well water testing along with full property reviews across the Mid-Missouri service area, and we follow CDC and EPA sampling guidelines so the lab results stay valid for real estate negotiations and health decisions.

Putting It All Together

A positive well water test is a warning that needs action, not a reason to panic. Stop drinking the water, switch to bottled or boiled water, shock chlorinate the system, fix any structural or source problems around the wellhead, and retest at a certified lab before going back to normal use. Coliform is a flag that something has a path into your well. E. coli is a direct warning of fecal contamination that needs immediate attention. The two big steps that solve most problems are sealing the well from outside contamination and disinfecting the system fully.

If your well has come back positive, or if you are buying a home with a private well and want to know what you are getting into, the team at ARC Home Inspections provides certified well water testing through accredited labs, paired with a full walk-through of the wellhead and property. We serve homeowners and buyers across rural Missouri who depend on private wells every day. Call us at 314-948-3058 to schedule a test and get clear, lab-backed answers about what is in your water.