Coliform Bacteria Contamination: Causes, How To Test For Bacteria, and Prevention

According to the U.S. Environmental Protection Agency, coliform bacteria are common in the environment and are generally not harmful. However, the presence of these bacteria in well water or spring water usually indicates that the water may be contaminated with germs that can cause disease and can even contaminate your well water without any change in taste or odor to the water. Therefore, the US EPA recommends annual testing of residential water wells for coliform bacteria.

What Type of Bacteria Should I Test For?

Generally, there are two categories of coliform bacteria that are found in well water, total coliform, and fecal coliform or E.coli. The presence of total coliform, by itself, doesn’t imply that the resource is contaminated, but it can reveal that one, if not more of the more serious types of harmful bacteria, such as fecal or E. coli bacteria, may be present. In many instances, whenever total coliform is detected, additional tests are performed to verify either the presence or absence of fecal or E. coli bacteria.

Simple Testing for Coliform At Home

Recently it has become possible to analyze for these bacteria at home utilizing state-of-the- art test kits. These kinds of low cost kits make it easy for anyone to keep an eye on their own home well drinking water supplies for contamination through consistent water testing of their water wells.

How Does Bacteria Contaminate Well Water?

Human or rodent waste products can be a principal source of bacteria in water. These sources of bacterial contamination consist of run-off from yards, feedlots, pastures, canine runs, and other farm land areas where animal wastes are deposited. Bugs, rats, rodents or wildlife entering the well can also be sources of contaminants.

hogs cause bacteria
Some other sources include leaking septic tanks, agricultural run-off, disposal of household chemical wastes, or flood events. Bacteria from these sources can enter wells which are open on the surface, do not have water-tight casings or caps, or do not have a seal of grout in the space (the space between the wall of the well and the outside of the well casing). Additionally, wells which have recently been worked on can be contaminated from the work done by the well driller or contractor. Introduction of coliform bacteria can occur from the tools that are used, drilling pipe, fluids used in the drilling, tools or dirt falling down into the well while it is being worked on, or even airborne particles being carried down into the well.

What Can I Do To Protect My Well From Bacteria?

contaminated well water
Your well should be constructed so that it is at least a foot above the surface of the ground or has a mound of dirt around it to ensure that rainwater or chemical run-off will not pool near your well and seep into it. Also if you are constructing a new well, it is important to minimize the proximity of possible sources of contamination – the further the better!

  • Septic Tanks, 50 feet
  • Livestock yards, Silos, Septic Leach Fields, 50 feet
  • Petroleum Tanks, Liquid-Tight Manure Storage and Fertilizer Storage and Handling, 100 feet
  • Manure Stacks, 250 feet

Be careful about storing or disposing household or lawn care chemicals and wastes or considering using organic alternatives which will break down before reaching your groundwater. Take steps to reduce erosion and prevent surface water runoff such as constructing a simple swale or using plants to stabilize slopes.

It is especially important to address these risks before they become an issue, and will help save money in the long run. Keeping up to date records of well installations, repairs, and water tests will help you keep ahead of potential issues.

More helpful resources about well water safety:

For more help on removing bacteria from your water, visit our Bacteria page on our Water Problems tab. If you still have questions, don’t hesitate to e-mail us at, leave us a message on Facebook, or use our online contact form for prompt, personalized assistance from our trained professionals.  Thanks for reading!

About the Author Gerry Bulfin

Need help with your well water? I have been assisting homeowners, small communities and businesses improve their well water quality since 1989. Please email me at if you have a question about water testing, test kits or well water systems in general. Gerry Bulfin CWS-IV Master Water Specialist WQA Certified Licensed California Water Treatment Contractor