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Changes in our source water (Lake Manassas, the Potomac River and Occoquan Reservoir), particularly in late summer and early fall, can lead to an earthy smell or taste in drinking water. This is due to increases in two naturally occurring compounds, geosmin and 2-Methylisoborneol (MIB).

In addition, changing temperatures can cause water in lakes to move from top to bottom, stirring up natural compounds. While some customers may find the smell or taste unpleasant, your water remains safe to drink.

Geosmin and 2‑Methylisoborneol (MIB) are naturally occurring, harmless organic compounds that can produce earthy or musty tastes and odors in drinking water.

Geosmin and MIB are produced by certain algae and soil‑based bacteria commonly found in lakes, rivers and reservoirs. Levels often rise in late summer and early fall when warm temperatures and slow‑moving water promote biological activity. 

Yes. Although the taste or odor may be unpleasant to some customers, geosmin and MIB are non‑toxic and do not pose any health risk. Their presence does not indicate contamination or a failure in water treatment.

Humans can detect geosmin and MIB at extremely low concentrations, making even trace amounts easy to smell or taste.

Heating increases the volatility of these compounds, meaning they enter the air more easily. This causes them to become more noticeable in showers or when preparing hot beverages.

Standard treatment processes remove algae and bacteria but not all dissolved geosmin and MIB. Utilities use activated carbon to greatly reduce levels, but small amounts may remain when natural concentrations are elevated.

Those who are sensitive to the smell and taste of geosmin and MIB may consider the following:

• Chill drinking water to reduce taste and odor.
• Add citrus to water for natural odor masking.
• Use an activated‑carbon filter for additional odor and taste removal.