Glass of Water

As water travels through the ground or over the surface, it dissolves naturally occurring minerals and radioactive materials and can absorb substances resulting from presence of animal or human activity.


Categories of substances that may be present in source waters include:

  • Microbiological substances

  • Inorganic substances

  • Pesticides and herbicides

  • Organic substances

  • Radioactive materials

Inorganic parameters – Physical/chemical

Physical/chemical parameters, for the most part, are naturally occurring in the source water. The water treatment process is designed to reduce the levels of these parameters.


Metals, for the most part, are naturally present in source water, or are the result of industrial activity. Some, such as copper and lead, may enter the drinking water from plumbing in the distribution system.

Taste and Odour

Taste and odour episodes in drinking water have become more prevalent in Ontario in the past five years. The cause is due to the decomposition of blue-green algae and generally occurs after the algae blooms in the late summer.

Special Health Concerns

Some people may be more vulnerable to contaminants in drinking water than the general population. Immuno-compromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants can be particularly at risk from infections. These people should seek advice about drinking water from their health care providers.

Hardness and Water Quality

Hardness is due to the presence of metal ions that come from minerals dissolved in the water. Hardness is based on the ability of these ions to react with soap, to form a precipitate or soap scum.

In fresh water, the primary ions are calcium and magnesium; however, iron and manganese may contribute to hardness.



Soft Water

0 to 17.1mg/L (0 to 1 grain/gallon)

Slightly Hard Water

17.1 to 51.3mg/L (1 to 3.5 grains/gallon)

Moderately Hard Water

51.3 to 119.7mg/L (3.5 to 7 grains/gallon)

Hard Water

119.7 to 179.55 mg/L (7 to 10.5 grains/gallon)

Very Hard Water

over 179.55 mg/L (over 10.5 grains/gallon)