If your tap water tastes earthy or musty this month, the explanation is the same as October: blue-green algae in Bushy Park Reservoir producing MIB and Geosmin compounds.
November is the second peak
CWS draws about 90 percent of its raw water from Bushy Park Reservoir. The warm-to-cool transition in fall triggers algae blooms that produce these naturally occurring compounds. October and November are the primary fall window. April and May are the spring window.
Harmless but noticeable
MIB and Geosmin are not health hazards at the concentrations detected in Charleston water. They're not regulated under the Safe Drinking Water Act. But humans can detect Geosmin at 5 to 10 parts per trillion, so even a trace amount registers as earthy or musty.
Who's affected and who isn't
CWS customers in West Ashley, James Island, and parts of North Charleston are affected. Mount Pleasant Waterworks blends CWS supply with deep aquifer groundwater. Summerville CPW is on a separate supply from Lake Moultrie and is not affected.
What to do
If the taste bothers you, a carbon-stage filter at the kitchen tap helps with aesthetic concerns. For a whole-home assessment, I'll test your water and identify which compounds are driving the taste.
Free water test. Call (843) 302-5720. I'll taste your tap with you.