Queen Quet, chieftess of the Gullah/Geechee Nation, has advocated for clean well water on St. Helena Island, South Carolina. (Photo by Bryn Caswell/News21)

The majority of the 43 million Americans who rely on private wells for their drinking water also use onsite sewage disposal systems known as septic systems. Septic systems rely on the earth to sanitize the water, but they’re complicated. In fact, many Americans don’t understand how they work. News21 reporter Bryn Caswell explains what these systems do and how they can contaminate drinking water.

To see the full News21 report on “Troubled Water,” go troubledwater.news21.com on Aug. 14.