Earthy and musty off-flavors in water occur worldwide, come from nature, and have no known health effects at their natural levels.
Earthy and musty odors can be found in natural waters and in soils, as well as in beets and corn (because they are grown in contact with soil). In waterways, when certain algae grow in abundance in what we call an algae bloom, high levels of these odors are produced. These taste and odor problems are sporadic and usually occur in the summertime when weather conditions are most likely to induce an algae bloom. The technical name for the chemicals produced by the majority of odor-causing algae is 2-methylisoborneol (MIB) and geosmin.
Helix uses ozone in the treatment process and one of its benefits is that it is very effective at removing earthy and musty flavors and odors. However, even at extremely low levels, such as 5 parts per trillion, highly sensitive people can still taste or smell them. When a large algae bloom occurs, more people detect an issue. A way of masking this harmless musty taste and odor is chilling your tap water.
Algae-related water quality issues usually clear up in a few days.