If your tap water tastes earthy or musty right now, you're probably on Charleston Water System. CWS draws roughly 90 percent of its raw water from Bushy Park Reservoir, which produces two naturally occurring compounds in spring and fall: MIB and Geosmin.
What causes the taste
MIB (2-methylisoborneol) and Geosmin are metabolic byproducts of blue-green algae (cyanobacteria) that bloom in the reservoir during warm-to-cool transition periods. April through May is the spring peak. October through November is the fall peak.
Both compounds are harmless at the concentrations detected. They're not regulated because they're not health risks. But humans can taste Geosmin at 5 to 10 parts per trillion, which means a trace amount produces a noticeable earthy or musty flavor.
Who's affected
CWS serves West Ashley, James Island, parts of North Charleston, and wholesale to Daniel Island and some Dorchester County areas. Mount Pleasant Waterworks blends CWS surface water with deep aquifer groundwater.
Summerville CPW is not affected. CPW sources from Lake Moultrie through Santee Cooper, a different watershed.
What you can do
A carbon-stage whole-home conditioner addresses chlorine taste. Whether it addresses Geosmin and MIB depends on the carbon contact time and media type.
Free water test. I'll taste your tap with you and tell you what I see. Call (843) 302-5720.