Your lab report has one word circled in red: “positive.” Coliform bacteria showed up in your well water, and now you’re standing in the kitchen wondering if it’s safe to make coffee.
Take a breath first. A positive result for coliform bacteria in well water is common, and for most homeowners in the Wenatchee Valley it’s a fixable, weekend-scale problem, not a disaster. But it’s also not something to shrug off. Coliform is a warning flag, and reading it correctly is the difference between a $30 fix and a water source you can’t trust.
This guide walks through what your specific result means, which numbers on the report actually matter, where the contamination is probably coming from, and what to do in the next 24 hours. We’ll also cover when a positive test points to something bigger than bacteria, and when it’s time to stop guessing and call a professional.
If you already know you need help sorting out a positive test, call us at (509) 351-8404 and we’ll walk through your specific report with you at no charge.
What a Positive Coliform Bacteria Test Actually Means
Coliform bacteria are a broad family of organisms that live in soil, plant matter, and the guts of warm-blooded animals. Most types found in nature are harmless to drink. The reason labs test for them isn’t because coliform itself makes people sick. It’s because coliform is easy to detect and it tends to show up whenever a pathway exists for surface contamination to reach your water.
Think of it like a smoke detector. The beeping isn’t the danger. It’s the signal that something is present that shouldn’t be, and it’s telling you to go find out what.
Most private well tests report on two or three categories, and the wording on your lab slip matters a lot:
- Total coliform positive, E. coli negative. The most common result. Something, usually surface water, soil, or organic debris, is getting into your well. It’s a real problem, but not an emergency.
- Total coliform positive, E. coli positive (or fecal coliform positive). This means fecal contamination, from animal or human waste, is reaching your water. This is the version that requires same-day action.
- Total coliform negative. Clean result. No action needed beyond your normal testing schedule.
If your report shows E. coli, stop drinking and cooking with the water right now, switch to bottled water, and don’t wait to see if a second test comes back different. That level of contamination carries real risk of gastrointestinal illness, and for kids, elderly family members, or anyone with a weakened immune system, it can get serious fast. Our emergency well service team fields these calls year-round, and we’d rather you call and it turn out to be minor than the other way around.
Total Coliform vs. Fecal Coliform vs. E. coli: Why the Wording Matters
Lab reports use these terms almost interchangeably in conversation, but they mean different levels of concern. Knowing the difference keeps you from either panicking over a minor result or brushing off a serious one.
| Result Type | What It Indicates | Urgency Level | Typical Next Step |
|---|---|---|---|
| Total coliform positive, E. coli negative | Surface water or debris intrusion; source is usually environmental | Address within days | Inspect wellhead, shock chlorinate, retest |
| Fecal coliform positive | Warm-blooded animal waste reaching the well | Address immediately | Stop drinking water, inspect for septic/animal source, shock, retest |
| E. coli positive | Confirmed fecal contamination, active health risk | Same-day action | Switch to bottled water, call a professional, shock and retest |
| Repeat positive after shock chlorination | Ongoing pathway, not a one-time event | Address before drinking resumes | Full wellhead and casing inspection |
Total coliform alone, without E. coli or fecal coliform, is by far the most common scenario on private wells around here. It usually traces back to something mechanical: a cracked well cap, a missing vent screen, or a casing seam that lets rain or snowmelt trickle down into the casing. It’s annoying, but it’s rarely a health crisis on its own.
This is also how the EPA’s own rules treat it. The federal Revised Total Coliform Rule uses total coliform as an indicator test precisely because it’s a reliable early warning for the presence of other, harder-to-test-for pathogens. You can read the full standard at the EPA’s page on the Revised Total Coliform Rule.
Where Coliform Bacteria in Well Water Comes From Around Here
North Central Washington throws a few specific risk factors at private wells that folks in other regions don’t deal with as often.
Spring snowmelt and irrigation season. When the Columbia River valley thaws out and orchard irrigation ramps up, ground saturation goes way up. Water that would normally soak into soil and get filtered instead runs across the surface, and any weak point at a wellhead becomes a direct path into the casing.
Older or buried wellheads. A lot of rural properties from Cashmere to Chelan still have wells set in pits or buried below grade, a common construction style decades ago that’s now known to be a contamination magnet. If your wellhead sits below ground level, that’s often the whole story right there.
Livestock and septic proximity. Washington code requires at least 100 feet between a well and a septic drainfield, but older properties were sometimes grandfathered in closer, and corrals or pastures uphill from a well can carry runoff straight to it.
A cracked or unsealed well cap. This is the single most common cause we find. A gap the size of a pencil is enough for insects, rodents, or surface water to get into the casing. We covered this in detail in our guide to well cap replacement.
The Washington Department of Health tracks coliform as one of the most frequently detected issues on private well tests statewide, and their guidance on interpreting bacteria results is worth a read if you want the full technical picture: doh.wa.gov.
Two Wells, Two Very Different Positive Tests
Denise bought a small acreage outside East Wenatchee last fall. The pre-purchase water test came back total coliform positive, E. coli negative. Her real estate agent had seen it before and wasn’t worried, but Denise wanted to understand why. A quick wellhead inspection found a hairline crack in the old concrete well cap, right where it met the casing. She had it replaced for $240, shocked the well the same afternoon, and her retest two weeks later came back completely clean. Total cost: under $300, and she closed on the house on schedule.
Tom and Linda’s story near Leavenworth went differently. Their well sits about 60 feet from a seasonal creek, and after a wet spring their annual test came back positive for both total coliform and E. coli. They stopped drinking the water immediately and switched to bottled water for the household, then called us the same day. We found the well pit itself was the problem: a buried, unsealed concrete pit that had been standard construction when the well was drilled in the 1980s. Converting it to a proper above-grade wellhead with a pitless adapter ran $2,100, on top of a shock chlorination and retest. Expensive compared to Denise’s fix, but it solved a problem that bleach alone never would have touched, since the pit itself was letting creek water in every time it rained.
Both households did the right thing: they tested, they took the result seriously, and they matched the fix to the actual cause instead of guessing.
What to Do in the First 24 Hours After a Positive Result
Your response should match your result. Here’s the practical order of operations.
If E. coli or fecal coliform is present: Stop drinking and cooking with the water immediately. Use bottled water. Don’t bathe infants in it. Call a professional the same day, especially if you can’t quickly identify an obvious cause like a recently opened well cap.
If total coliform alone is present: You don’t need to panic, but don’t ignore it either. Boiling water for one minute will kill coliform bacteria if you need drinking water in the short term, which is the opposite of the nitrate situation, where boiling makes things worse. Then move on to finding and fixing the source.
Either way, inspect the wellhead first. Before you do anything else, walk out and look at the cap, casing, and surrounding grade. Cracks, gaps, standing water near the wellhead, or a cap that isn’t sitting flush are the most common culprits and often the cheapest to fix.
Retest to confirm. Labs occasionally produce false positives from sampling technique, especially if the collection bottle or tap wasn’t handled correctly. One positive result is a reason to act, but if the fix seems too easy, a second sample confirms you’re chasing the right problem. A basic lab test runs $25 to $50 if you collect the sample yourself. If you’d rather have it done right the first time, our full water testing service, including sampling and a plain-English walkthrough of the results, runs $150 to $400 depending on what panel you need.
Don’t sit on a positive result while you decide what to do. Request a free estimate here and we’ll help you figure out whether you’re looking at a cap replacement, a chlorination job, or something bigger, before you spend money on the wrong fix.
Fixing It: Shock Chlorination, Prevention, and When It’s Not Enough
For the majority of total coliform positives, especially the kind Denise had, the standard fix is shock chlorination: dosing the well with a strong chlorine solution, letting it sit for 12 to 24 hours, then flushing it out. Done correctly, it costs about $30 in supplies and takes a weekend.
We’ve written a full step-by-step walkthrough of the process, including bleach dosing by well depth and exactly how long to wait before retesting, in our guide to shock chlorination for wells. If you’re comfortable with basic wellhead work and the cap isn’t damaged, that guide has everything you need.
Shock chlorination is a one-time disinfection, though, not a permanent fix. It kills what’s in the water today. It does nothing about a cracked cap, a buried pit, or a septic system too close to the wellhead, the way Tom and Linda’s pit was letting creek water in with every storm. If your well tests positive again after a proper shock, you don’t have a bacteria problem anymore. You have a pathway problem, and that calls for a physical inspection, not more bleach.
For households that want ongoing protection rather than periodic shocking, an ultraviolet disinfection system installed at the point of entry runs $800 to $1,500 installed and treats every gallon that enters the house continuously. We cover how that technology works in our guide to UV treatment for well water.
Preventing Repeat Positives
Carlos, who lives on a small orchard near Chelan, shocked his well three times over two summers, and it kept coming back positive for total coliform every few months. By the time he called us, he’d spent close to $150 on bleach and test strips with nothing to show for it. A wellhead inspection found the culprit in about ten minutes: a missing vent screen that let rain and insects straight into the casing. A $180 cap and screen replacement, followed by one final shock chlorination, ended it. He hasn’t had a positive test in over a year.
A few habits keep most wells out of this cycle entirely:
- Inspect your wellhead every spring, before irrigation season saturates the ground. Look for cracks, gaps, and standing water pooled against the casing.
- Test annually, and always after any work that opens the well, a new pump, pressure tank swap, or cap replacement.
- Know your setbacks. Keep septic drainfields, livestock, and fertilizer storage well clear of the wellhead.
- If you’re buying a property on a shared well, get bacteria results in writing before closing. Our guide to shared wells in Washington covers what to check before you sign.
If your home is on a well and you’ve never had a full water test, or it’s been more than a year, don’t wait for symptoms or stains to prompt you. Our well water testing guide for the Wenatchee area covers what to test for and how often, and buyers should also see our well inspection guide for home buyers before closing on any property with a private well.
When to Call a Professional Instead of DIYing It
Shock chlorination and a wellhead inspection cover most positive coliform results. Call a licensed well professional instead of handling it yourself when:
- E. coli or fecal coliform shows up, especially if you can’t identify an obvious cause within a day.
- The well tests positive again after a proper shock and 7 to 14 day wait, which points to a structural pathway rather than a one-time event.
- The wellhead is buried, in a pit, or the cap is corroded shut. Prying on stuck hardware or working in a confined pit is exactly how people get hurt.
- Anything involves the electrical connections at the wellhead. The wiring for your pump runs right through that area, and it’s not a DIY zone.
- You’re on a shared well and need to coordinate testing, treatment, or repairs with other households.
We service wellheads, casings, and treatment systems across Chelan, Douglas, and Grant counties, including repair work tied to contamination issues through our well pump repair service. Most wellhead defects that cause repeat coliform positives, cracked caps, bad seals, missing screens, cost far less to fix than the ongoing frustration of a well that never tests clean. Call (509) 351-8404 and we’ll give you a straight answer about what your specific report means and what it’ll take to fix it. Estimates are always free, and we’re licensed and insured in Washington.
Frequently Asked Questions
Is it safe to drink well water with a positive coliform test?
It depends on which result you got. If E. coli or fecal coliform is present, stop drinking the water immediately and switch to bottled water until the problem is fixed and a retest comes back clean. If only total coliform is positive, boiling the water for one minute makes it safe to drink short-term while you find and fix the source.
How do I get rid of coliform bacteria in my well water?
Shock chlorination is the standard fix for most cases: a strong chlorine dose, a 12 to 24 hour wait, then a thorough flush. It costs about $30 in supplies for a typical residential well. If the well tests positive again afterward, the real problem is usually a physical entry point, like a cracked cap or damaged casing, that needs to be found and repaired before bleach will hold.
How long does it take to fix coliform bacteria in well water?
A straightforward case, like a cracked cap causing total coliform without E. coli, usually resolves in about two weeks: a day to inspect and repair the wellhead, a day to shock chlorinate, several days to flush and let chlorine clear, then a 7 to 14 day wait before the confirming retest. Cases involving a buried well pit or septic contamination take longer, since physical repairs are involved.
Can coliform bacteria in well water make you sick?
Most coliform bacteria found in nature won’t make a healthy adult sick on their own. The real danger is what a positive result signals: a pathway that could also be letting in E. coli, viruses, or other pathogens. That’s why any positive result, especially one that includes E. coli or fecal coliform, should be treated as a signal to act, not ignored just because you feel fine today.