Water Quality Update: Understanding Changes in Taste and Odor
Published on November 10, 2026
Some Superior residents have noticed an earthy or musty taste and smell in their drinking water. We understand these changes can be concerning and want to reassure residents that the Town's drinking water remains safe to drink.
Recent testing has detected geosmin, a naturally occurring compound found in surface water, which Town staff believe is the likely cause of these changes. While geosmin can affect how water tastes and smells, it is not considered harmful and does not indicate pollution or a problem with the safety of the water.
What's geosmin?
Geosmin is produced naturally by certain algae and bacteria in water. It creates an earthy smell similar to soil after rainfall. Geosmin also occurs naturally in familiar foods, including beets, carrots and mushrooms.
According to the World Health Organization (WHO), geosmin is not considered a health hazard at concentrations regularly found in drinking water. Although it can noticeably affect taste and smell, WHO classifies geosmin as an aesthetic concern rather than a direct public health issue, and it has not established a health-based drinking water limit for the compound.
People are particularly sensitive to the tastes and smells geosmin though, and some people notice it more than others, even in extremely small amounts. The smell may also become more noticeable when water is heated, such as during a shower or when making coffee or tea.
Recent testing detected geosmin at 44 nanograms per liter in untreated water and 28 nanograms per liter in treated water. These are extremely small concentrations, but people can detect geosmin at levels as low as 5 nanograms per liter. For comparison, 28 nanograms per liter is equivalent to a concentration of less than one drop of water per Olympic-sized swimming pool.
Geosmin is more common during warmer months, when conditions encourage algae growth. This year's drought and warmer water may have contributed to the changes residents are experiencing. Other Colorado communities have reported similar concerns.
What is the Town doing about it?
Although the water remains safe to drink, we recognize that unpleasant tastes and odors can be frustrating, especially for those who are more sensitive to them.
Town staff are working with water treatment operators to address these concerns. As part of this work, a contractor is replacing the activated carbon used in the Water Treatment Plant's filtration system. This material helps remove compounds like geosmin that affect the taste and smell of drinking water. The replacement is expected to be completed by the end of November.
In the meantime, refrigerating drinking water or using a water filter containing activated carbon may help reduce the unpleasant taste and odor.
The Town will continue monitoring water conditions and working to improve the taste and odor of our drinking water.
While the Town’s water meets all regulatory requirements and is safe to drink, if you do experience any water quality concerns you can report them on Superior Click Fix or by emailing the Public Works Department at pwu@info.superiorcolorado.gov.