Water Testing For Bacteria, Algae, Viruses, Protozoa, Fungi and other Microorganisms

Does well water have bacteria?

Yes, nearly all groundwater and surface water samples are likely to contain various species of naturally occurring microorganisms. Fortunately, most such bacteria (and other microorganisms) are non-pathogenic (meaning, they don’t make you sick). However, some bacteria in water can make you very sick. Laboratory testing focuses on these species and genera in particular: Coliform, E. coli, legionella, H. pylori and cryptosporidium, for example.

What kind of bacteria are found in well water?

Heterotrophic bacteria are commonly found in soil and therefore very common in well water. Most heterotrophs, fortunately, are part of earth’s natural biota and are non-pathogenic.

What bacteria should I test for?

While it can be very expensive to test for ALL bacteria, a subset of bacteria, called Coliform bacteria are good indicators of sanitary water safety. Coliform bacteria are good indicators of overall bacteria water safety because they don’t normally live deep underground (preferring instead the top layers of the soil). If coliform bacteria do show up in a water test, this indicates some surface contamination and that pathogenic (or disease-causing) microorganisms may also be present. 

How to test my well water for bacteria?

Laboratory testing is by far the most reliable and effective way to test for chemistry and bacterial contamination. Test strips can be very unreliable. Because it is expensive and impractical to lab test your water for all pathogenic bacteria and microorganisms, it’s recommended that you consider testing for one or a few of the packages on this page. Common tests include Coliform & E. coli , Legionella, HPC, Iron-related bacteria, slime forming bacteria and Total Microbiology tests. 

Lab water testing for bacteria

There are many laboratory methods for testing bacteria. The most common quantitative methodologies include: Most Probable Number (MPN) and Membrane Filtration (MF). However, the US EPA and most other regulatory bodies rely on Presence / Absence methods (or P/A) because they are generally more accurate, faster and lower cost. Colilert and Colitag are the two most popular such tests. 

Coliform water test

Colilert and Colitag are the two most popular lab tests for coliform and E. coli in water.

E. coli water test

Because all E. coli are coliform bacteria, an E. coli test is run after a coliform test produces a detection. Similar to total coliform testing, E. coli analysis is often performed by Colilert or Colitag.

Coliform in drinking water limits

The US EPA maximum contaminant level (MCL) for coliform in drinking water is zero (no coliform) in a 100ml sample.

E. coli in drinking water limits

The US EPA maximum contaminant level (MCL) for E. coli in drinking water is zero. After treatment there should be no E. coli in a tested water sample. 

What do you do if you have bacteria in your well water?

For most types of bacteria, chlorine, UV, and other specially designed water treatment systems can disinfect water and kill 99%+ of the microorganisms–including coliform and E. coli bacteria. Other microorganisms like viruses and protozoa (i.e. cryptosporidium) are more chlorine-resistant and may need more specialized treatment.

My well water tested positive for coliform

(1) Use boiled or bottled water from a safe alternative source for cooking and drinking until you can fix the issue. Note that if you have other chemical issues with your water (like arsenic, lead or nitrates) then boiling your water can unfortunately increase these concentrations and cause health problems. (2) Perform a chlorine disinfection or chlorine “shock” to kill the coliform bacteria in your well. You can do this yourself or contact a licensed well contractor. 

Is it safe to drink water with coliforms?

Even though most coliform bacteria are non-pathogenic, it is not safe to drink water with coliform bacteria contamination. Presence of coliform bacteria means that there is a likelihood of pathogenic microorganisms in the water, as well. 

Bacteria in water symptoms

Disease-causing microorganisms can cause diarrhea, cramping, nausea, vomiting, headache, fever, fatigue and even death. Young children and elderly populations, as well as those with weakened immune systems are more likely to get sick from microorganisms in water.