Millions of people across the US use well water, but very few test it often enough to make sure it’s safe

Serious water contaminants such as nitrate may not have any detectable taste or odor. Willie B. Thomas/Digital Vision via Getty Images

About 23 million U.S. households depend on private wells as their primary drinking water source. These homeowners are entirely responsible for ensuring that the water from their wells is safe for human consumption.

Multiple studies show that, at best, half of private well owners are testing with any frequency, and very few households test once or more yearly, as public health officials recommend. Even in Iowa, which has some of the strongest state-level policies for protecting private well users, state funds for free private water quality testing regularly go unspent.