Cisterns are watertight containers to protect and store drinking water. In some circumstances, the water from a cistern may not be safe to drink.
If cistern collars, lids, fill ports, or screened vents are damaged, germs (contaminants) may get in. If the cistern structure is damaged (e.g., frost, settling), cracking below the surface may happen, which could let contaminated groundwater and soil in. Cisterns in areas at risk for floods may also be at risk of overland flooding from surface water. If you see any areas that germs could get in or your test results show the water is contaminated, it’s important to fix the problem.
Once the contamination problem is fixed, follow the steps below to clean and disinfect your cistern. You’ll need to arrange to have an approved water hauler on-site before this. You need clean, safe water to clean and disinfect a cistern.
The Provincial Laboratory for Public Health (ProvLab) tests private water drinking water systems for bacteria. However, the ProvLab can’t test water for every type of harmful germ.
The ProvLab does 2 standard tests (total coliforms, E.coli) on water samples. These results will show how likely the water is to be contaminated with bacteria. Coliforms are a group of bacteria that are found everywhere (e.g., soil, on plants, lake and river water). People and animals have E. coli bacteria in their bowels and stool.
Test your cistern:
If you know the water is contaminated (e.g., you see rodents in the cistern), clean and disinfect it right away. You don’t need to test the water first.
Current as of: March 13, 2018
Author: Environmental Public Health, Alberta Health Services
This material is for information purposes only. It should not be used in place of medical advice, instruction, or treatment. If you have questions, talk with your doctor or appropriate healthcare provider. This information may be printed and distributed without permission for non-profit, education purposes. The content on this page may not be changed without consent of the author. Contact email@example.com.