Total Coliform Bacteria

The Total Coliform Bacteria test is used to check the sanitary quality of drinking water. According to the EPA, good drinking water should be absent of all Coliform bacteria. “Coliforms” is a group of bacteria made up of primarily 18 different bacteria. Coliform bacteria are not harmful in most cases, but if they are present in your water supply it is an indicator that other harmful and disease causing bacteria may have also entered your drinking water supply.

When Coliform bacteria are present in a water supply, it is considered to be a potential health hazard and is classified as unsafe for human consumption. It is important to know that the Coliform test gives no indication if the water is chemically safe to drink.

E. Coli is one of the members of the Coliform group. It is a fecal bacteria which comes from the intestines of warm-blooded animals. The test shows the difference between E. Coli and other Coliforms. Drinking water is considered to be an “Extreme Health Hazard” when E. Coli is present.

The laboratory results are reported as Coliform Absent or Coliform Present. Absent means that Coliforms WERE NOT present in the sample. Present means that Coliforms WERE present in the sample. E. Coli Absent or E. Coli Present is also reported. If the sample is Absent for Coliform, it will also be Absent for E. Coli.

If Coliforms are present and E. Coli is absent, then the water is considered unsafe and a potential health hazard. When both Coliforms and E. Coli are present, the water is deemed to be an extreme health hazard.

If a water system contains Coliforms, shock chlorination is usually the first step to eliminating it. NRC provides written instructions for how to perform this procedure. After the chlorination procedure is done on the system, ensure the system is used for a minimum of 5-7 days to ensure the chlorine has washed through and retest. Coliform analysis should be performed at least every six months.