How to Read Results

Total Coliforms (TC) are a collection of relatively harmless bacteria that occur naturally in soil and decaying vegetation, but may also be found in human or animal faeces.

E.coli is a family of bacteria that is commonly found in the intestines of warm-blooded animals.  There are many different types of E.coli.  Most are harmless to people, but there are some that can cause enteric symptoms such as diarrhea, cramps, nausea, and vomiting. When symptoms are severe they can lead to extreme dehydration and for the vulnerable, more serious complications such as Hemolytic Uremic Syndrome.  An example of this harmful bacterium is E.coli O157: H7.  This was one of the bacteria found in the water supply that resulted in the Walkerton tragedy.

Overgrown (abbreviated on the lab result form as O/G) is the term applied when there are too many background bacterial colonies, making it impossible to accurately determine the number of Total Coliforms or E.coli.

Interpretation of Lab Results

The only acceptable level of bacteria is 0. Low total coliform results coming from a secure well represent a low risk. Higher counts or counts from a well subject to surface water contamination indicate a higher risk to health.

Precautionary measures include not using the water for drinking, brushing teeth, making juice, ice or formula, washing fruit and vegetables that won't be boiled and washing dishes unless the water has first been boiled or comes from another safe source.

Corrective measures may include repairs to well covers, drainage diversion, well and plumbing disinfection, installation of a permanent treatment system or putting in a new well.

Total Coliforms are harmless bacteria but their presence may indicate that the water supply is not secure or that the sample was mishandled or contaminated. The lab will report counts up to 80; after that, all counts are reported as >80 (greater than 80).

• To be prudent, no TC count should be ignored.
• Low TC counts that come from a protected source like a drilled well should be confirmed with a careful resample before proceeding with corrective measures.
• Low TC counts that come from a dug well or other source that may be subject to surface water contamination should result in precautionary and corrective measures right away.
• Higher Total Coliform counts from any source should result in both precautionary and corrective measures.
• Any Overgrown report should immediately result in precautionary measures followed by corrective measures, and resampling.
• Any E. coli count should immediately result in boiling the water for at least 1 minute, followed by corrective measures.