What are waterborne microorganisms?
Microorganisms are life forms too small to see with the naked eye. In drinking water, three groups matter most: bacteria, protozoa, and viruses. Some are harmless. A few cause serious illness. And many can enter your water supply without changing its taste, smell, or color at all — which is exactly what makes them dangerous.
Bacteria
0.2 – 10 microns
Protozoa
2 – 50 microns
Viruses
0.004 – 0.1 microns
Bacteria in your water
Bacteria are single-celled organisms found everywhere on Earth, typically measuring about 0.2 to 10 microns. Most are harmless, and some are even beneficial, helping break down organic matter. But a small group causes disease.
The ones we test for are coliform bacteria — a broad family that includes E. coli (Escherichia coli). E. coli lives naturally in the intestines of humans and warm-blooded animals, so finding it in your water is a red flag for sewage or fecal contamination.
Here's the key point many homeowners miss: coliform bacteria themselves are usually harmless. We don't test for them because they'll make you sick — we test because their presence proves there's a pathway for disease-causing germs to enter your well or plumbing. If coliform can get in, so can pathogens.
It's also worth knowing that the absence of coliform doesn't guarantee perfectly clean water. Other contaminants can still be present, which is why a complete water analysis looks at more than one indicator.
Protozoa and parasites: Giardia and Cryptosporidium
Protozoa are single-celled organisms that live mainly in water, and several are well-known parasites. The most important in drinking water are Giardia and Cryptosporidium.
These parasites form cysts (Giardia) and oocysts (Cryptosporidium) — tough protective shells that let them survive in harsh conditions, including in chlorinated water. When swallowed, they hatch in the intestines and cause giardiasis and cryptosporidiosis, both marked by watery diarrhea, cramps, and dehydration.
According to the CDC, Cryptosporidium is the leading cause of waterborne disease in the United States, and giardiasis is the most commonly reported parasitic illness in the country. Young children and people with weakened immune systems are most at risk.
The good news: these cysts are relatively large (roughly 2 to 50 microns), so the right filtration removes them. Standard pitcher and refrigerator filters often don't — but a properly specified reverse osmosis system does, which is why RO is considered the gold standard for protozoa protection at home.
Viruses in water
Viruses are the smallest infectious microorganisms — only about 0.004 to 0.1 microns across, hundreds of times smaller than bacteria. They're so tiny they can slip through filters that block bacteria entirely.
Viruses can't multiply outside a living host, but they're hardy: they survive freezing and drying, and they spread through the feces of infected people and animals. This is another reason fecal indicator bacteria like E. coli matter — their presence signals that viruses and other pathogens may have entered the same water source.
Why Southwest Florida water is especially at risk
Shallow aquifers
Permeable sandy soil moves contaminants underground fast.
Warm climate
Microbes stay active all year, multiplying year-round.
Storms & flooding
Hurricane-season rain pushes runoff into wells.
When groundwater rises after a storm, it makes more direct contact with private wells and can carry in septic leakage, fertilizer runoff, and stormwater debris. A well that tested clean last year can become contaminated within days — long before anyone notices a change in taste or smell.
That's why the Florida Department of Health strongly recommends testing private wells at least once a year for bacteria and nitrate, and after any flooding event. Lee County's health department even offers bacteriological testing for well owners. If your home in Cape Coral, Fort Myers, or Naples runs on well water, annual testing isn't optional — it's basic protection.
City water vs. well water
City (Municipal) Water
Disinfected with chlorine or chloramines before it reaches your home. Controls bacteria but introduces taste, odor, and skin-and-hair concerns — and doesn't stop chlorine-resistant Cryptosporidium.
Private Well Water
Receives no disinfection. Whatever is in the ground comes out of your tap — higher risk of bacteria, parasites, iron, sulfur, and sediment in our region.
Either way, the only way to know what's actually in your water is to have it tested.
How to find out what's in your water
You can't diagnose microbial contamination by sight, smell, or taste. A professional in-home water test is the fastest way to see exactly what you're dealing with.
Inti Water's WQA-certified specialists test water across Cape Coral, Fort Myers, and Naples every day. We come to your home, test on the spot, and explain every result in plain English or Spanish — with no obligation and no sales pressure. You keep the report and decide what to do next.
How to protect your home
UV disinfection
Neutralizes bacteria and viruses without chemicals — ideal for wells.
Removes sediment, iron, and sulfur and improves overall water quality.
Reduces dissolved solids and removes protozoa cysts and other contaminants for clean water at the tap.
The best choice depends on your water source and what your test reveals — which is exactly what a free water analysis is for.