What Do Coliform Bacteria in Water Mean?

The EPA says total coliforms are a group of related bacteria that are, with few exceptions, not harmful to humans, but that it considers them a useful indicator of other pathogens, the bacteria, parasites and viruses that can cause health problems if people ingest them in drinking water. It says it published the Revised Total Coliform Rule on February 13, 2013, revising the 1989 Total Coliform Rule to improve public health protection, and that the rule sets a maximum contaminant level goal and maximum contaminant level for E. coli to protect against potential fecal contamination, along with a treatment technique requirement for total coliforms.

The CDC advises private well owners to test their well water at least once every year for total coliform bacteria, nitrates, total dissolved solids and pH level. After a well is disinfected, it says to boil the water at a rolling boil for 1 minute, or use another water source, until the water has been tested, and to wait at least 7 to 10 days after disinfection. It says that if results show no total or fecal coliforms, the water can be considered safe to drink, and that owners should follow up with more tests in the next 2 to 4 weeks and again in 3 to 4 months. The CDC says boiling is the best way to kill germs in water, and advises using bottled, boiled or treated water when tap water may not be safe.