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Changes in Taste and Odour of Tap Water

Occasional changes in the taste and odour of drinking water is not a threat to public health

From time to time some residents may notice changes in the taste or odour of their drinking water. These changes are most often a musty / earthy taste or odour to their drinking water or a noticeable increase in the taste / odour of chlorine. Depending on the cause, these tastes and odours could persist in drinking water for a couple of weeks.

Many municipalities in Ontario, like Niagara, which get their water supply from surface water sources experience this problem periodically. While changes in the taste and odour may be unpleasant for some with a sensitive sense of taste and smell, these changes only affect the aesthetic qualities of the water and doesn't impact water safety.

Causes of taste and odour changes

Taste and odour occurrences are caused by a couple different factors. One factor is the seasonal biological changes in the source water, which produces odour-causing chemical compounds, called geosmin and 2-methylisoborneol. Even very tiny concentrations of these compounds can result in the earthy / musty taste and odours in water.

Standard lab tests detect limits for both of these compounds at three parts per trillion but some people can taste / smell them at concentrations of one part per trillion. Some can detect these changes even when levels are so low they are undetectable through standard testing.

The second factor is changes to drinking water treatment processes in response to changing source water conditions, such as an increase in water temperature, which requires higher levels of chlorination to treat.

During these episodes, tap water supplied by the municipal water supply systems remains safe to drink. Our water treatment plants are designed with processes to reduce the effects of taste and odour, but these may not eliminate it entirely.

Ways to reduce tastes and odours

Residents who experience taste and odour issues with their tap water can use water pitcher filter systems, such as a Brita to help reduce or eliminate the tastes and odours. Storing water in a loosely sealed glass container in the refrigerator for a period of time before drinking can also help.

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