Coliform Bacteria Testing: Why do it, How to do it, & How Often?

Health authorities strongly recommend annual coliform bacteria testing for private water wells as contamination can occur without any change in taste or odor to the water.  There are many ways that well water can become contaminated by coliform bacteria, but it is most important to test:

• Once a year for all private residential water wells
• After a new well has been constructed
• After recent work has been done on the well
• If you suspect or see any indication that contamination has taken place, such as if the well was covered with flood water.

What Is Coliform Bacteria?

Generally, there are two categories of coliform bacteria that are found in well water, total coliform, and fecal coliform or E.coli.

Total coliforms are found naturally in the environment and are found in the soil, in water that has been influenced by surface water, and in human or animal waste. 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.

Fecal coliforms are the group of the total coliforms that are considered to be present specifically in the gut and feces of warm-blooded animals and are considered a more accurate indication of animal or human waste than the total coliforms.

Escherichia coli (E. coli) is the major species in the fecal coliform group and is considered to be the best indicator of fecal pollution and the possible presence of pathogens. Most coliform bacteria do not cause disease.

However, some rare strains of E. coli, particularly the strain 0157:H7, can cause serious illness. Recent outbreaks of disease caused by E. coli 0157:H7 have generated much public concern about this organism. E. coli 0157:H7 has been found in cattle, chickens, pigs, and sheep. Most of the reported human cases have been due to eating undercooked hamburger. Cases of E. coli 0157:H7 caused by contaminated drinking water supplies are rare.

What Should I Test For?

Testing for bacteria is the only reliable way to know if your water is safe. You cannot tell by the look, taste, or smell of the water if disease-causing organisms are in it. It is recommended that well owners test their water for coliform bacteria at least once a year and more frequently if bacteria has been a problem in the past.

Frequently, concentrations of pathogens from fecal contamination are small, and the number of different possible pathogens is large. As a result, it is not practical to test for pathogens in every water sample collected. Instead, the presence of pathogens is determined with indirect evidence by testing for an “indicator” organism such as coliform bacteria

The most basic test for bacterial contamination of a water supply is the test for total coliform bacteria. Total coliform counts give a general indication of the sanitary condition of a water supply.

Which Test Kit Do I Need?

The at-home test is an easy, fast, and effective method for determining if your well water has coliform and E.coli or not. When using this simple test the media turns blue-green in the presence of coliform bacteria.

Also, our UV light works great with the Coliform Bacteria EZ Cult 24 Hour Test to test for coliform bacteria.

When using this simple test, the sample turns blue-green in the presence of coliform bacteria, but E. coli growth is confirmed by blue fluorescence under UV light. Simply shine the UV light on the sample to see if E.coli is present.

For more extensive or state required testing (such as applying for a new daycare center license) we recommend the Watercheck which offers Professional EPA-certified laboratory results available for the fraction of the cost of regular laboratory testing.

How Do I Collect a Water Sample For The WaterCheck?

• Wash your hands with soap and warm water.
• Take the sample from a cold water tap. Use a tap without a screen or remove the screen before you collect the sample.
• Let the cold water run constantly for at least 2 minutes before you collect the sample.
• Hold the bottle near the base of the tap to get the sample. Fill it past the 200 mL mark (to the shoulder of the bottle). Do not overfill the bottle.
• Put the cap on the bottle right away. Make sure the cap is secure, but do not over-tighten it.
• Put the identification label from the requisition form on the bottle.

Fill out the requisition form and include the information below. If you miss anything on the requisition, your sample might not be processed.

• Name and daytime phone number
• Mailing address and postal code
• Collection site (e.g., kitchen sink)
• Legal land description and/or civic address
• Date and time sample was collected
• Name of person who collected the sample

On the requisition form, write down if this is a re-sample. You also need to fill out section A (Drinking Water) and add any comments or special requests at the bottom of the requisition.

• Put the sample and requisition form in the plastic bag that came with the sample bottle.
• Put the sample in a cooler filled with ice packs and bring it to a drop-off location near you right away, or if sent by express, use overnight next day morning option.

Note: Samples must be collected from the cold water supply line. do not:

• Rinse the sampling bottle
• Let water overflow or splash down the side of the bottle
• Put the cap on a countertop (it can get contaminated)
• Open the bottle until you are ready to collect your sample
• Touch the inside of the cap, mouth, or neck of the bottle
• Collect samples from a garden hose, outside tap, or other places that might be dirty

 When Should I Test and How Often?

Late spring or early summer are the best times to test your well, since coliform contamination is most likely to show up during wet weather. Whether your test results are positive or negative, understand that the sample you collected is just a “snapshot” of your well's water quality. The more samples you have tested, the more confident you can be about the quality of the water you are drinking.

What Do The Results Mean?

If coliform bacteria are present in your drinking water, your risk of contracting a water-borne illness is increased. Although total coliforms can come from sources other than fecal matter, a positive total coliform sample indicates the possibility of pollution in your well. Positive fecal coliform results, especially positive E. Coli results, should be considered an indication of fecal pollution in your well.

What Should be Done if Coliform Bacteria are Detected in Your Well?

If E.coli or fecal coliform are detected in the drinking water, the first step should be an emergency chlorination, which can last two to five days. At the same time a system is being disinfected, it is recommended to vigorously boil the drinking and cooking water for one minute before using it.

It is also very important to continue testing the water because if anything happens to the chlorine residual, or if the chlorine-demand changes and the consumer doesn’t know about it, the water can become unsafe again. However, If fecal coliform or E. coli are detected in well water, the first step should not only be to disinfect your system but to identify the source of your bacteria contamination.

What Kinds of Defects Can Allow Contamination?

• A missing or defective well cap – seals around wires, pipes, and where the cap meets the casing may be cracked, letting in contaminants
• Contaminant seepage through the well casing – cracks or holes in the well casing allow water that has not been filtered through the soil to enter the well. This seepage is common in the wells made of concrete, clay tile, or brick
• Contaminant seeping along the outside of the well casing – many older wells were not sealed with grout when they were constructed
• Well flooding – a common problem for wellheads located below the ground in frost pits that frequently flood during wet weather.

Long-Term Options for Dealing with Bacterial Contamination of a Well

• Connecting to the regional public water system, if possible
• Inspecting wells for defects and repairing them if possible
• Constructing a new well
• Installing continuous disinfection equipment
• Using bottled water for drinking and food preparation

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 [email protected], leave us a message on Facebook, or use our online contact form for prompt, personalized assistance from our trained professionals.  Thanks for reading!