Coliform Bacteria Testing
To find out if there is any Coliform in your drinking water you should contact an accredited water testing laboratory (look in Yellow Pages under ‘laboratories’).
The laboratory will supply you with the special sampling bottles and the instructions. To take a sample in a correct way, remember:
- do not rinse the sampling bottle
- wash your hands before taking a sample
- then, remove the sterile strap from the bottle
- remove faucet screen, hoses and aerators form the end of the faucet
- disinfect the faucet by dipping the end in the bottle full of bleach
- run cold water for 5 minutes
- turn the water down and fill in the sample bottle up to the fill line only. Do not overfill or underfill
- screw cap on tightly
- fill in paperwork and keep a copy for your records
- send the sample to the laboratory.
Samples
must be kept cool and delivered to the laboratory within 24 hours. It is highly advisable for all private water systems to be sampled at least once or twice per year, or whenever there is a reason to believe that the water supplies may have become contaminated ( e.g. after flooding).
Before consuming water from a new well, disinfect and flush the entire system and then sample for Coliform bacteria.
When water is tested for Coliforms, the results are usually given as the number of colony forming units per 100mL of water sampled (CFU/100mL).
In Canada, the maximum acceptable concentration (MAC) for Coliform bacteria in drinking water is 0 colony forming units per 100mL. That means for every 100 mL of drinking water tested, no total Coliforms or E.coli should be detected.
When drinking water is tested for total Coliforms and E.coli and it is safe to drink, the results may be presented in different formats, as:
- absent
- 0 colony forming units per 100 milliliters (0CFU/100mL)
- less than 1 colony forming unit per 100 milliliters (<1CFU/100mL)
- non-detect (ND)
- 0 most probable number per 100 milliliters (MPN/100mL)
If Coliform bacteria are detected in drinking water, the source of contamination should be immediately investigated.
