POSITIVE BACTERIA TEST? START HERE.
If your test just came back positive, start here.
Total coliform is an indicator — it means a pathway exists for surface contamination to reach your water. E. coli is more specific: it points to human or animal waste reaching the supply.
Use bottled water, or water brought to a rolling boil for one minute, for drinking, cooking, ice, coffee, baby formula, and brushing teeth — until the problem is corrected and follow-up testing is clear.
Three different jobs: disinfect what is already in the system, repair how it got in, then treat continuously. UV alone does none of the first two.
Switch to bottled water, or water brought to a rolling boil for one minute, for anything that goes in your mouth. Pennsylvania guidance covers drinking, cooking, food preparation, dishwashing, ice, coffee, baby formula, and brushing teeth.
Washing dishesWash with soap and water, then rinse with clean — bottled or boiled — water.
ShoweringAdults can shower without swallowing the water, then wash hands with soap and clean water.
Young childrenUse a sponge bath so they do not accidentally swallow any.
Labs report these differently, and the difference decides how fast you need to move.
A broad group living in soil, plants, and surface water. Mostly harmless themselves — but their presence means a pathway is open, and whatever opened it could let something worse through.
A subgroup tied to the digestive tracts of people and warm-blooded animals. Suggests contact with waste rather than just soil or vegetation.
One type of fecal coliform, and the strongest warning of the three. A positive result means fecal contamination has likely reached the water supply.
Why annual testing is not optional here.
The highest private-well population of any state — and the state does not regulate them.
From Penn State’s analysis of thousands of Pennsylvania private wells and springs.
Same dataset. Roughly one in seven of the wells tested.
Almost always through a physical pathway — not from the aquifer itself. The usual suspects are a loose or non-sanitary well cap, cracked casing, ground that slopes toward the well instead of away, a shallow or older well, nearby septic, or recent pump and plumbing work.
Southwestern PA adds its own factor. Our fractured shale and sandstone can move water fast, so after heavy rain or flooding surface water reaches a compromised well far quicker than it would through deep soil filtration.
It can also come from inside: contaminated household plumbing, a failed treatment component, or a sample collected the wrong way.
GET MY WATER FIXEDSix steps, in this order. Skipping any of them is how positives come back.
The response sequence
Bottled or boiled water for all oral uses while the result is investigated.
Review the sample point, collection method, and property history — a bad sample is a real possibility.
Cap, casing, grading, recent flooding, plumbing work, and existing equipment.
Shock chlorination to clear what is already living in the well and lines.
Repair the pathway once it is identified. This is the step most often skipped.
Confirm with follow-up testing, then add continuous treatment when conditions justify it.
About retesting timing
There is no single correct retest date. PA DEP’s disinfection procedure says wait until the chlorine has cleared, then wait another two to five days. PA Department of Health guidance describes retesting ten to fourteen days out when judging whether an event was temporary. The right date depends on the disinfection method, how fast chlorine clears, and what your lab specifies — so we coordinate the sample timing with the laboratory rather than applying one universal waiting period.
They are not competing options. They do different jobs, and most positives need more than one.
| Response | What it does | What it does not do |
|---|---|---|
| Bottled or boiled water | Protects the household right now | Nothing about the well itself |
| Shock chlorination | Disinfects bacteria currently in the well and plumbing | Does not stop it coming back in |
| Well or plumbing repair | Closes the pathway contamination used | Does not disinfect what is already there |
| UV treatment | Continuously treats water passing through the chamber | Does not repair the well or remove chemical contaminants |
| Continuous chlorination | Ongoing disinfection with a measurable residual | Requires chemical feed, contact time, and monitoring |
| Retesting | Verifies the water at that point in time | Treats nothing on its own |
Water flows through a stainless chamber past an ultraviolet lamp at roughly 254 nanometers. That wavelength damages the genetic material inside susceptible microorganisms so they can no longer reproduce — which is what makes them incapable of causing infection.
UV adds no salt and no routine chemicals, and it does not change taste, odor, or pH. It also does not filter anything out — organisms stay in the water, inactivated.
Class ABuilt for water that is not microbiologically safe — a positive well test. Failsafe dose of 40 mJ/cm².
Class BSupplemental only, for water already deemed safe. 16 mJ/cm² — not the right answer after a positive result.
UV depends on light reaching the organism. Anything that blocks, absorbs, or coats gets in the way.
| What is in the water | Why it defeats UV | What has to happen first |
|---|---|---|
| Sediment / turbidity | Particles cast shadows — organisms ride through untouched | Fine sediment filtration ahead of the chamber |
| Iron | Bakes an opaque coating onto the quartz sleeve | Iron treatment at the point of entry |
| Manganese | Same fouling problem, at even lower concentrations | Manganese treatment upstream |
| Hardness | Scale forms an insulating film on the sleeve | Softening or conditioning first |
| Low UV transmittance | Dissolved organics absorb the light before it works | Measure UVT and size the chamber to it |
| Sulfur, low pH, lead, PFAS, nitrate | UV does nothing for any of these | Separate treatment — UV is disinfection only |
This private well is exactly why UV cannot simply be bolted on. Alongside the bacteria, the raw water carried iron at 33× the fouling threshold and manganese at 100× it — plus 21 gpg hardness and visible cloudiness. Every one of those would have coated the quartz sleeve or shadowed the organisms.
| Measured | Before (Jul 19) | After (Jul 27) |
|---|---|---|
| Iron | 10 ppm | Below the field method’s 0.05 mg/L reporting limit |
| Manganese | 5 ppm | Below the field method’s 0.05 mg/L reporting limit |
| Hardness | 21 gpg | Below 1 gpg |
| Turbidity | Slightly cloudy | Clear — no sediment |
| TDS | 881 ppm | 759 ppm |
Every claim on this page traces back to a primary source — regulators, accredited standards bodies and state public-health guidance.
Reviewed July 2026 by Lance Cesare, third-generation water-treatment specialist. Water testing referenced on this page is on-site field analysis performed by Cesare’s Quality Water Solutions. Coliform and E. coli results require an accredited laboratory and are not published from field methods.
Get a professional water analysis and a custom treatment plan—clear answers, no pressure.
